FOUS11 KWBC 262025
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
325 PM EST Wed Nov 26 2025

Valid 12Z Wed Nov 26 2025 - 12Z Sat Nov 29 2025


...Significant winter storm with localized blizzard conditions will=20=20 continue to impact parts of the Upper Midwest/Great Lakes through=20
Wednesday as lake effect snow intensifies into Thanksgiving and=20
Friday for the eastern Great Lakes...

...Confidence increasing on a second winter storm to affect the
Northern Plains Friday and the Midwest/Great Lakes Friday night=20
into Sunday...


...Key Messages for both systems are in effect and linked below...


...Great Lakes...=20
Days 1-2...

Strong surface cyclone, 991mb over the central U.P. of Michigan
this afternoon has a well- defined axis of deformation situated=20
over western portions of Lake Superior down through Wisconsin.=20
Peak cyclone intensity is now with a gradual occlusion phase
expected as it shifts east tonight. Powerful north to northwest=20
flow will continue to spread in behind the system making for
prolific lake effect snow (LES). This remains downwind of Lake=20
Superior through the overnight period with heavy snowfall=20
situated across all of the Michigan U.P. and the heaviest focused=20
across the the area from Ironwood over to Marquette. Lake effect=20
snows will increase over western lower Michigan through this
evening as WSWly flow veers to WNWly and increasing cold air
advection. General persistence in the flow coupled with multiple=20
shortwave perturbations moving around the periphery of the ULL=20
positioned over the U.P. and adjacent Ontario will maintain to a=20
multi- band structure downwind of Lake Michigan. Strongest bands=20
will likely reside off northern Lake Michigan down through Traverse
City with hi-res CAMs and Canadian Regional highlighting heavy
narrow banding (nearly single banding) from Lake Superior and
northern Lake Michigan fetch to the area northwest of Gaylord
through Thursday night. LES threat diminishes Friday as the flow
decreases with the low approaches the Gulf of St. Lawrence.=20

Downstream of the eastern Lakes of Erie and Ontario, persistent=20
LES pattern will ensue this evening behind the swift moving cold=20
front with snow formation across both lakes by midnight.=20
Prevailing southwest flow off Lake Erie will kick off the banding=20
along the southern periphery of the Lake up through the eastern=20
regions before manifesting into a more consolidated band structure=20
as it drifts south overnight. Winds will veer more out of the west=20
and northwest by Thursday afternoon with the banding positioning=20
becoming more pronounced off the southern periphery of Erie leading
to several inches of snow falling in the adjacent terrain downwind
of the Lake. Lake Ontario will see a similar pattern with=20
southwesterly flow veering back west in a similar time scale. This=20
will lead to areas of the Tug Hill and places downwind of the Lake=20
off I-81 seeing the initial heavy LES signature, eventually with=20
the banding shifting towards the southeast side of Lake Ontario.=20
Initial indications are for a long- fetch connection between Huron=20
and Ontario could enhance banding downwind of the lake on Friday=20
leading to several inches of snowfall across the southern portions=20
of the Tug Hill and points south and west.=20

WPC probabilities for an additional 8 inches of snow after 00Z=20
Thursday are at least 50% over much of the U.P. of Michigan (except=20
for areas closer to Lake Michigan), northwest Lower Michigan, far-=20 northeastern Ohio, northwestern PA, southwestern NY, and around the=20
Tug Hill Plateau. Within these regions, there is a smaller but still=20 significant area of probabilities between 40-70% for 18 inches of=20
snow. Isolated totals could exceed 30 inches, including what has=20
already fallen across the Michigan U.P. Best chances are likely over=20
the western U.P. terrain, areas downwind of Lake Michigan and=20
Traverse Bay, I-90 corridor along the southern lake shores of Erie,=20
and the Tug Hill down through Oswego county in western New York=20
state.

Travel will be difficult and perhaps impossible at times due to snow-
covered roads, blowing snow, and low visibility.

Kleebauer/Jackson


...Northwest to Montana...=20
Days 1-2...

Developed low arrives to the WA Coast early Thursday with elevated
snow levels dropping to around 5000ft in the Cascades through the=20
day Thursday. Day 1.5 snow probs for >8" are 30-60% for the higher
WA Cascades.=20

An approaching shortwave trough descends Alberta Thursday night=20
and meets this low over ID/western MT on Friday. This combined=20
trough expands over the northern Rockies on Friday, promoting=20
downstream lee-side cyclogenesis near the eastern WY/CO border=20
Friday morning. 1040mb+ surface high pressure following from Canada
will help support some lower- level upslope-enhanced snow over=20
western MT where snow could be heavy at times over the Lewis Range=20
around Glacier NP particularly Thursday night. Day 2 WPC=20
probabilities for >8" snow are 50 to 80% over the northwestern MT=20
ranges down to the Bitterroots.

The arrival of Arctic air Thursday night allows snow for the
valleys/Plains of northern MT through Friday. Banding intensifies=20
north of the developing surface low with sfc-850 troughing and WAA
enhancing rates across northern MT through Friday morning with
lighter snows for the rest of the state into Friday evening. Day 2
snow probs for >6" are 20-50% over north-central MT.=20


...Northern Plains through the Midwest...
Days 2/3...

A low level frontogenetical band will set up along the baroclinic
zone northeast of the developing low Friday. Expect moderate to
locally heavy snow to establish in an ever expanding swath of snow
across southwest ND and much of SD Friday, reaching central Iowa by
Friday evening. 3-6" snowfall can be generally expected through
this band with locally higher amounts possible given slow motion
away from its orientation allowing some prolonged snowfall.

By early Saturday, the upper trough will push onto the High Plains,
the surface low is well developed over southern KS with an inverted
trough extending northeast to Wisconsin. Broad cyclonic flow around
this trough with Gulf- sourced moisture allows for rapid expansion
to the precip shield Friday night/Saturday with ample cold air for
snow both on the WAA ahead of the low/ and through the entire back
side/comma head. Broad coverage of moderate to heavy snow develops
Friday night over eastern SD/southern MN/northern IA with expansion
east to lower Michigan then through Saturday. A strong pressure
gradient will make for blustery conditions. Probabilities for
notable snow continue to increase with current Day 3 WPC snow probs
for >8" 40-75% over southern MN down through central Iowa with a
contour of 40% >6" snow from far eastern SD clipping northeast Neb
and including much of northern IL, southwestern WI, and up to the
Twin Cities in MN.



The probability of significant ice across the CONUS is less than=20
10 percent.

Jackson


...Winter Storm Key Messages are linked below...

Lake Effect Snow:

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!-l_s6iqeeDLG8U0cpRm4Ugv_XIj_L2CQQzY8a-JrBs0c_= c23jxXUqD4At1cseASflzM56Gg8cSClQJW3ckc29S1aTEE$=20

Northern Plains through Midwest System Friday-Sunday:

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!-l_s6iqeeDLG8U0cpRm4Ugv_XIj_L2CQQzY8a-JrBs0c_= c23jxXUqD4At1cseASflzM56Gg8cSClQJW3ckc2aqw0z4A$=20



$$

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FOUS11 KWBC 270840
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
340 AM EST Thu Nov 27 2025

Valid 12Z Thu Nov 27 2025 - 12Z Sun Nov 30 2025

...Great Lakes...=20
Days 1-2...

Long duration and impressive lake effect snow (LES) event ramps up
today and continues through Friday with prolific snowfall totals
likely in the favored snow belts SE of the Lakes.

This event is driven by a large closed 500mb low which will be over
southeast Ontario to begin the period. This low will spin nearly in
place through this evening before secondary vorticity energy
rotating into its base helps pivot it off to the east on Friday. A
final piece of energy, a strung-out vorticity lobe, will then move
across the Great Lakes Friday aftn, pulling the entire system to
the east and resulting in warm-to-neutral temperature advection by
Friday night, bringing an end to this event.

With strong cyclonic flow covering the region, NW winds will bring
strong cold advection (CAA) across the lakes to produce this
impressive LES. 850mb temps are progged to fall to -10C to -15C,=20
which when moving across lake temperatures that are still generally
+6C to +10C according to GLERL, will produce increasingly steep=20
lapse rates, SBCAPE as high as 800-1000 J/kg, and inversion depths
potentially reaching 700mb from the surface. This all will support
intense snowfall rates for which both the HREF and WPC snowband
tool suggest will reach 1-2"/hr within narrow bands, and locally
heavier snowfall rates cannot be ruled out.

While the bands may twist and pivot at times due to wind
fluctuations, in general they should be pretty persistent and
focused across the northern U.P and far NW L.P. of MI through
Friday morning, with more focused and longer-duration bands
impacting the Chautauqua Ridge and Tug Hill Plateau into Friday
night. This will result in storm total snowfall that has a high
probability (>70%) of exceeding 12 inches near Traverse City, MI,
as well as east of Lakes Ontario and Erie. Locally, more than than
2 feet of snow is possible (10-30% chance according to WPC=20
probabilities) across the Chautauqua Ridge and Tug Hill Plateau.

Key Messages remain in effect for this system, and are linked below
(Key Message #1).


...Northern High Plains through the Great Lakes...
Days 1-3...

...Significant winter storm likely to impact portions of the
Northern Plains, Upper Midwest, and Great Lakes through this
weekend...

A closed low off the WA coast will dive rapidly southeast while
opening, reaching the Northern Rockies by Friday morning. This wave
interacting with a stationary front draped across the region and a strengthening upstream jet streak will help spread precipitation
into the High Plains of MT very late D1 into D2 (around 12Z
Friday). Temperatures will be plenty cold for all snow as
precipitation continues to expand into the Dakotas, and the
evolution of this shortwave will drive the stationary front
southward as a cold front, leading to even colder temperatures and
dry fluffy snow into D2. Ascent during this period will be
generally modest, but as snowfall expands, WPC probabilities
suggest a moderate risk (50-70% chance) for at least 4 inches of
snow from northeast Montana through eastern South Dakota. This
jet-streak forced band has intensified in recent model progs, so
locally heavier snow is possible, especially across South Dakota
where a stripe of 700-600mb fgen gets intensified through the jet
structure.

Thereafter, the system amplifies to become much more impressive=20
with expanding heavy precipitation into the Upper Midwest Friday=20
night through Saturday. The mid-level trough diving into the=20
Central Plains will sharpen, and as the vort swings into the base=20
of the longer wave trough it will force a negative tilt coincident=20
with the development of coupled jet streaks (one strengthening over
the Central Plains and another exiting the Great Lakes) to produce
robust ascent. This overlapping synoptic lift will help strengthen
a surface low developing in the lee of the CO Rockies and then=20
tracking east, and eventually northeast, from KS through IL and=20
into MI by 12Z Sunday.

Downstream of this surface low, warm and moist advection will
rapidly intensify as 850mb winds surging to above 50kts draw
elevated PWs northward from the Gulf, reflected by PW anomalies
surging above the 90th percentile according to NAEFS into KS/MO/IA.
This will be accompanied by a theta-e ridge lifting northward as
well, and although a true TROWAL is not currently progged, this
theta-e ridge will still promote additional moisture and some
elevated warm air to promote modest potential instability. This
evolution suggests intense WAA, which is reflected as well by model
output, which will help expand precipitation from the Dakotas and
Iowa Friday night, to encompass most of the Upper Midwest Saturday,
and then reach the Great Lakes Saturday night.=20

As far as snowfall amounts and impacts, there is still considerable
uncertainty due to model placement and timing of this system. In
general, the models are in good agreement with the large-scale
evolution, but with such strong WAA in place, even minor timing or
latitudinal differences can result in significant changes to
impacts. Evaluation of D3 and D4 clusters suggests the GEFS is
potentially a bit under-dispersed with its faster trough
progression, while the ECENS/CMCE feature more spread to support a
variety of solutions suggesting a continued ensemble approach
especially by D3. However, some condensing of the spread D2 boosts
the confidence that light to moderate snow will expand into the
Corn Belt before 12Z Saturday, before pushing east thereafter.

In general, this event appears to be of longer-duration with=20
moderate snowfall rates driven by 280-290K isentropic ascent
combined with modest fgen beneath the weak theta-e ridge aloft.=20
However, as is the case with most strong WAA events, a narrow=20
corridor of heavier snowfall with rates greater than 1"/hr appears=20
likely, especially near MO/IA where conditional instability is in=20
place and strong fgen drives lift into the DGZ. The DGZ appears to=20
be elevated and shallow in most places (although some SREF=20
probabilities for 100mb of depth do eclipse 30%), but locally some=20
banding could produce more intense rates leading to more=20
substantial amounts and impacts.

Currently, WPC probabilities are extremely high (>90%) for more
than 4 inches in a large swath from eastern SD through most of IA,
northern IL, southern WI, and into parts of lower Michigan.
However, the axis of heaviest snowfall is likely from southern IA
through western Michigan, where WPC probabilities are high (>70%)
for more than 8 inches of accumulation, and locally 12+ inches of
snow is possible, and there are several members within the WSE
plumes which indicate more than 15 inches in some areas. The exact
placement of the heaviest snow is still in question due to a=20
continued southern trend in guidance, but the long duration of this
event, combined with locally heavier snow rates, leads to high=20
confidence in an impactful event. This is additionally reflected by
WSSI-P probabilities which exceed 90% (50%) for moderate (major)=20
impacts for portions of IA, IL, and WI. Post-Thanksgiving travel is
likely to be extremely disrupted during this event.

Key Messages are in effect for this system and are linked below
(Key Message #2).


...Cascades and Northern Rockies...=20
Days 1-2...

Closed mid-level low west of WA will push onshore Thursday evening
while opening into a shortwave as it lifts into the Northern
Rockies. Downstream of this impulse, modest warm and moist
advection will surge IVT to above 250 kg/m/s into the Cascades,
leading to increasing coverage and intensity of precipitation. Snow
levels will climb to around 6000 ft within this IVT plume, but then
crash quickly as the cold front accompanying this system pushes
east as well. At the same time, a secondary front will dig
southward from Alberta, Canada into the Northern Rockies, and
westerly flow aloft pushing higher moisture into this region will
interact with the terrain and this front to produce ascent and
expanding precipitation. At the same time, the overlap of the
strongest height falls downstream of the filling shortwave with an
amplifying jet streak will likely cause surface low development
Friday morning, helping to additionally enhance ascent before
everything kicks off to the east by Friday night.

This evolution will likely cause moderate to at times heavy snow
(heaviest in the Northern Rockies due to fgen and upslope
enhancement), with snow levels fluctuating around 3000-4000 ft, but
remaining near the surface east of the Continental Divide and into
the High Plains. WPC probabilities are moderate (>50%) for 4+
inches D1 across the Cascades, but high (>70%) for 6+ inches near
Glacier NP and the surrounding Northern Rockies. During D2 snowfall
shuts off across the Cascades, but continues in the Northern
Rockies with an additional moderate chance (50-70%) for 6+ inches
of snow again. Travel across most of the Northern Rockies passes
will likely be impacted during this snow.


The probability of significant ice across the CONUS is less than=20
10 percent.

Weiss


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!71PkPC9AEcSguo65jYfOcG0iB12Z-tOnE0FjdAaVTtrFj= 3ARvInbHUaxEL7Y-FFu1kMuU5m89_2mgxWYr5rimWePIrw$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!71PkPC9AEcSguo65jYfOcG0iB12Z-tOnE0FjdAaVTtrFj= 3ARvInbHUaxEL7Y-FFu1kMuU5m89_2mgxWYr5riXp5Fw8Y$=20


$$

=3D =3D =3D
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FOUS11 KWBC 272050
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
350 PM EST Thu Nov 27 2025

Valid 00Z Fri Nov 28 2025 - 00Z Mon Dec 01 2025

...Great Lakes...=20
Day 1...

Long duration lake effect snow (LES) event continues through=20
Friday with prolific snowfall totals in the favored snow belts for
NWly flow in northern MI and for WNWly flow off Lakes Erie and
Ontario.=20

Deep low remains over central Quebec through Friday before lifting
to Labrador. The mid level trough axis associated with the low is
currently over the eastern U.P. and will swing east over the
eastern Lakes tonight. Saturated DGZ zones will maintain efficient
snow production over the autumnally warm lakes. Ridging finally=20
spreads east over the region Friday night ending the LES.=20

For Michigan expect individual banding in NW flow over the eastern
U.P. with additional banding from added fetch from Lake Michigan=20
into the Tip of the Mitt will persist through Friday morning. Day=20
1 WPC snow probs for >8" additional are 40-70% in the same narrow=20
zones being impacted now.=20

Eastern Great Lakes see ideal multiple lake fetch in cyclonic flow as
seen in current radar mosaics with banding from Superior,=20
Michigan, Huron, and Ontario into the Tug Hill and fetch from
Superior, lower Michigan, and Erie into the Chautauqua Ridge of
western NY and east of Cleveland. WPC Day 1 snow probs for >8"
additional are 50-70% for these features, and over 80% on the
Chautauqua Ridge where probs for >12" are 50-70%.

Key Messages remain in effect for this system (link #1 below).


...Northern High Plains through the Midwest into the Northeast...=20
Days 1-3...

...Significant winter storm to impact large portions of the=20
Northern Plains, Midwest, and Great Lakes through this weekend...

A closed low along the WA coast this afternoon will shift southeast
tonight while opening, crossing the Northern Rockies Friday. This=20
wave is shunted on the southern trajectory from a northern stream
trough currently shifting south down the Canadian Rockies tonight.
This trough interaction and a strengthening upstream jet streak=20
will help spread moderate snow bands from Glacier NP through
northern MT tonight. Temperatures will be plenty cold for all snow
in the bands with some freezing rain potential on the southern
portions of precip over south-central MT overnight.=20

The frontogenetical banding quickly extends across the Dakotas
Friday morning, reaching western Iowa in the afternoon. This
banding is north of a developing lee-side low ahead of the merging
troughs that develops over eastern CO Friday and shifts east over
the KS/OK border as it further develops Friday night. This allows
the fgen band to transition into a deformation band around an
inverted trough extending from the surface low. Day 1.5 snow probs
for >6" are 30-60% from Northeast MT through central Iowa.=20

Thereafter, the system amplifies to become much more impressive=20
with expanding heavy precipitation through the central Midwest=20
Friday night through Saturday. The mid-level trough diving into the
Central Plains will sharpen, and as the vort swings into the base=20
of the longer wave trough it will force a negative tilt coincident=20
with the development of coupled jet streaks (one strengthening over
the Central Plains and another exiting the Great Lakes) to produce
strong ascent. This overlapping synoptic lift will help strengthen
a surface low developing in the lee of the CO Rockies and then=20
tracking east, and eventually northeast, from KS through IL and=20
into southern MI by 12Z Sunday.

Downstream of this surface low, warm and moist advection will
rapidly intensify as 850mb winds surging to above 50kts draw
elevated PWs northward from the Gulf, reflected by PW anomalies
surging above the 90th percentile according to NAEFS into KS/MO/IA.
This will be accompanied by a theta-e ridge lifting northward as
well, and although a true TROWAL is not currently progged, this
theta-e ridge will still promote additional moisture and some
elevated warm air to promote modest potential instability. This
intense WAA will help expand precipitation from the Dakotas and=20
Iowa Friday night, to encompass most of the Upper Midwest Saturday,
and then cross Lower Michigan Saturday night before surging up the
Interior Northeast Sunday.

Confidence continues to increase in the track of the low with a
preference for the northern end of the precip shield given to the
EC/GFS which are farther north (through central WI with 0.5" QPF) than
the CMC/UKMET. The broad precip shield and ample cold air will
result in pivoting heavy bands with the highest totals as of now
forecast over central IA where a foot is possible. As noted before
the DGZ depth will be a concern at times and with so much precip
from WAA, the ratios should be somewhat limited over IL/IN ahead of
the system.=20

Day 2/2.5 WPC snow probs for >8" are over 30% from far southeast
SD/northeast Neb across all but far southwest IA, southern MN,
central and southern WI, and northern IL. Day 3 probs for >8" are
20-40% for much of the L.P. of Michigan. Post-Thanksgiving travel=20
is likely to be extremely disrupted during this event.

Key Messages remain in effect for this system (Link #2 below).


...Cascades and Northern Rockies...=20
Days 1-2...

Low crossing WA tonight with snow levels in the Cascades around
5000ft. Pacific moisture surges inland ahead with snow levels over
the northern Rockies of 4000-5000ft which decrease after snow
tapers behind a northern stream trough descending from the Canadian
Rockies. Day 1 snow probs for >6" are 40% in the high WA Cascades=20
and 50-80% across all western MT ranges into northern ID.=20

A combined upper trough shifts down the Rockies Friday with Day 1.5
snow probs for >6" 40-70% in the Tetons, Absarokas, Bighorns, and
ranges of north-central C0.=20


Jackson



...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!8umiVbKQN4ZSupkAbsvNAy8egWLsRvjnEIX-waL1s0UKs= _UdFepA7tN5qL700FGj-H401SxDmvGxZyaBuiBN2o7Ywhc$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!8umiVbKQN4ZSupkAbsvNAy8egWLsRvjnEIX-waL1s0UKs= _UdFepA7tN5qL700FGj-H401SxDmvGxZyaBuiBN6Di-u1E$=20




$$

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FOUS11 KWBC 280707
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
207 AM EST Fri Nov 28 2025

Valid 12Z Fri Nov 28 2025 - 12Z Mon Dec 01 2025

...Great Lakes & Northeast...=20
Day 1...

Cyclonic flow aloft will persist a long duration lake effect snow
(LES) event into Saturday morning, with prolific snowfall totals
likely in a few areas.=20

The period begins with an elongated but closed mid-level low
centered over Quebec driving lowered heights into the Northeast.
Rounding the base of this trough, a secondary shortwave and
elongated vorticity lobe will swing eastward through the Great=20
Lakes and into the Northeast tonight, bringing a brief period of=20
shortwave ridging to the area tonight. This will be the evolution=20
to finally shut off the LES.

However, until then, two significantly impactful winter weather
areas are expected. The first is in the favored WNW snow belts off
the Great Lakes: from the eastern U.P. through the NW L.P. of MI,
and then downstream along the Chautauqua Ridge and the Tug Hill
Plateau. 850mb temps falling to as low as -15C (-10C far east
portions) will drive steepening lapse rates across lake
temperatures that are still generally +6C to +10C according to
GLERL. The cooling column will keep the DGZ relatively shallow, but
favorable ascent crossing the DGZ efficiently will produce bands of
very heavy snow for which the HREF indicates has a >60% chance of
exceeding 1"/hr, and will likely reach 2-3"/hr at times in response
to deep inversion depths as high as 700mb. Although winds will
fluctuate just enough to prevent stationary single bands (plus the
fetch direction is not along the long-breadth of the lakes in many
areas), narrow corridors of heavy snow are expected, especially
where any upstream connection can occur from Huron/Superior/Georgian
Bay to Lakes Erie and Ontario. The heaviest snow is likely D1 just
southeast of Lakes Erie and Ontario where WPC probabilities for 8+
inches reach 50-90%, and storm total snowfall from this event=20
could be over 2 feet in a few locations.

In addition to the LES, a strong cold front pressing east from the
Lakes early this morning will reach the Atlantic coast this=20
evening. The guidance has become increasingly excited in the
potential for convective snow showers or snow squalls along this
front, as reflected by a snow-squall parameter well above 1. The
environment appears favorable for snow squalls from western PA
through northern ME as the front passes east, moving across an
environment with SBCAPE as high as 250 J/kg coincident with modest
0-2km fgen and theta-e lapse rates falling below 0C/km. Moisture
may be the limiting factor away from the Great Lakes, so the best
chance for squalls appears to be well inland of these states, but
any place that does receive a squall this afternoon would likely
experience dangerous travel due to rapidly changing conditions with
briefly heavy snow and gusty winds.

Key Messages remain in effect for this system (link #1 below).


...Northern High Plains through the Midwest into the Northeast...=20
Days 1-3...

...Significant winter storm to impact large portions of the=20
Northern Plains, Midwest, and Great Lakes through this weekend...

The first widespread significant winter storm of the season begins
in earnest today as a positively tilted shortwave trough emerges
from the Pacific Northwest and tracks southeast into the
Northern/Central Plains. As a secondary vorticity impulses rotates
into the trough, this will force downstream amplification of the
mid-level pattern, resulting in a negatively tilted trough and
increasing ascent downstream into the Upper Midwest and Great
Lakes. At the same time, jet streaks both upstream and downstream
of this amplifying trough will begin to couple, producing even more
intense deep layer lift, and a surface low will result - first in
the lee of the Rockies and then tracking gradually northeast into
MI by Sunday morning. This low will then continue to deepen as it
shifts across southeast Canada and exits into the Canadian
Maritimes by the end of the forecast period /12Z Monday/.

The guidance has come into much better agreement with the track and
intensity of this system, and while small temporal and spatial
differences among the ensembles still exist, the spread is minimal
compared to previous model runs leading to higher confidence in the
evolution. As the low deepens and moves northeast, impressive WAA
will develop downstream of the developing cyclone, spreading PWs
which will exceed the 90th percentile northward into MO/IA. The
accompanying theta-e ridge will surge in tandem and isentropically
ascent the region, and while guidance is still not suggesting a
strong TROWAL, at least subtle warm air aloft will help develop
modest conditional instability. The coincident and impressive 290K
isentropic ascent will lead to expanding and intensifying
precipitation, with moderate snow likely across much of the
Northern Plains, Upper Midwest, and Great Lakes, especially Friday
night through Sunday morning.

On D1, the heaviest snowfall accumulations are likely in a narrow
band driven by the jet streak aloft and the accompanying
ageostrophic/fgen enhancement between 700-600mb. This will cause a
stripe of periodically heavy snow from southern ND through western
IA, and although the band should be narrow, snowfall rates of
0.5"-1"/hr are likely which could cause 4-6" of snow as reflected
by WPC probabilities for 4+ inches that reach above 70%.

However, the most significant part of this event begins late D1
across IA and then spreads east through D2 into MI. Here, the
impressive isentropic ascent will be quite moist as reflected by
mixing ratios of 4 g/kg on the 290K surface, leading to a rapidly
saturating column. While in general this upglide will result in
moderate snowfall rates, there appears to be an increasing risk for
heavier snowfall across portions of MO/IA/IL as the WAA forces
an increasing isothermal layer beneath the DGZ which also begins to
deepen. Cross-sections are more robust featuring a corridor of
folding theta-es surfaces within the elevated RH, suggesting a
greater potential for CSI and convective snowfall rates. There is
still some uncertainty into this since this signal is much more
robust tonight than previous model runs, but locally 1-2"/hr rates
appear possible which is supported by the WPC prototype snowband
tool despite a modest overall appearance of the evolution with
respect to conceptual models for heavy snow bands. Still, multiple
bands lifting northward for a long duration will result in
significant snowfall accumulations and major impacts for the post-
Thanksgiving holiday travel.=20

This will be a significant system with several waves of moderate to
heavy snowfall. On D2, the heaviest accumulations are expected from
far eastern NE through IA, northern IL, and southern WI. WPC
probabilities in this region are 70-90% for more than 6 inches of
snow, and locally as high as 50% for more than 12 inches, highest
near the Quad Cities of IA. Later D2 into D3 the heaviest snow
shifts eastward and eventually wanes in intensity, but additional
heavy snowfall exceeding 6" is possible, especially around Lake
Michigan and into the L.P. of MI. Event total snowfall may reach
15" in isolated locations Saturday.

Moderate snowfall is also expected across the interior northeast=20
where WPC probabilities D3 are as high as 50-70% for 4+ inches in=20
the higher terrain of VT, NH, and ME.

Key Messages remain in effect for this system (Link #2 below).


...Central Rockies...
Day 3...

A potent shortwave will drop out of the Pacific Northwest Sunday
morning and then move progressively southeast, reaching the Four
Corners Sunday night while maintaining a positive tilt. Late D3
this feature will begin to sharpen, with the resulting downstream
jet streak intensifying into the Central Plains. The overlap of the
RRQ of this jet streak with the greatest height falls ahead of the
trough axis will help spawn low pressure in the Great Basin, and
this low will help to increase ascent across the Central Rockies
Sunday evening. As the overall ascent increases, precipitation will
expand, and periods of moderate to heavy snow are likely, generally
above 5000 ft. This system is expected to remain progressive so
prolonged snowfall is not expected, but WPC probabilities indicate
a moderate risk (50-70% chance) of at least 6 inches of snowfall
across the CO Rockies and northern San Juans, with lighter
accumulations expected as far west as the Wasatch of Utah.


Weiss




...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!6Sc2F0cnium5fdExFU2gmXHPKlYB1f8bP0Ql_VmqDRwDR= tO2_L40P2nqWm2GPccQ_EI7PVD0CcUgKaNs5dlLL32TFvQ$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!6Sc2F0cnium5fdExFU2gmXHPKlYB1f8bP0Ql_VmqDRwDR= tO2_L40P2nqWm2GPccQ_EI7PVD0CcUgKaNs5dlLAcOrDGE$=20



$$

=3D =3D =3D
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FOUS11 KWBC 281854
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
154 PM EST Fri Nov 28 2025

Valid 00Z Sat Nov 29 2025 - 00Z Tue Dec 02 2025

...Great Lakes & Northeast...=20
Day 1...

Persistent cyclonic flow will maintain the current long duration=20
lake effect snow (LES) event into Saturday morning leading to prolific
snowfall totals likely in a few areas.=20

Elongated but closed mid-level low remains centered over Quebec=20
driving lowered heights into the Northeastern CONUS. Rounding the=20
base of this trough, a secondary shortwave and elongated vorticity=20
lobe is swinging eastward through the western Great Lakes,
eventually making headway into the Northeast tonight, bringing a=20
brief period of shortwave ridging to the area overnight. This will=20
be the evolution to finally shut off the LES machine that's been=20
present the past 48+ hours.

However, until that transpires, two significantly impactful winter
weather areas continue through this afternoon and early evening.=20
The first is in the favored WNW snow belts off the Great Lakes:=20
from the eastern U.P. through the NW L.P. of MI, and then
downstream along the Chautauqua Ridge and the Tug Hill Plateau. 18z mesoanalysis indicates a broad expanse of 850mb temps between -10
to -15C, driving steepening lapse rates across lake temperatures
that are still generally +6C to +10C according to GLERL. The
cooling column will keep the DGZ relatively shallow, but favorable
ascent crossing the DGZ efficiently has aided in producing a
plethora of multi-band structures with hourly rates upwards of
1"/hr. Hourly max rates will likely reach 2-3"/hr at times in
response to deep inversion depths as high as 700mb, especially in
the singular band structure from a long fetch axis oriented from
Lake Huron down through Georgian Bay then back over Lake Ontario.
The aforementioned persistent singular band is well-defined at this
hour off Lake Ontario through Oswego county extending into=20
southern Tug Hill and areas downstream. This area will exhibit the=20
heaviest snowfall accumulations through the period with areas=20
residing in the band likely to attain well over 12" at this=20
juncture leading to snowfall totals eclipsing 2ft for the entirety=20
of the event.

In addition to the LES, a strong cold front pressing east from the
Lakes has allowed for convective snow showers or snow squalls=20
along this front. Regional radar composite shows a multitude of
convectively based snow showers/squalls across southern NY state
down through western and central PA. The environment remains
favorable as the front advances east with MUCAPE as high as 200=20
J/kg coincident with modest 0-2km fgen and theta-e lapse rates=20
falling below 0C/km centered over west-central PA as of 18z. Snow
squall warnings have been issued in response over the past few
hrs, a testament to the environmental favor in place. Any area that
receives these snow squalls will encounter the opportunity for=20
dangerous travel due to rapidly changing conditions with briefly=20
heavy snow and gusty winds.

Key Messages remain, but will be the final issuance for the event=20
(link #1 below).


...Northern High Plains through the Midwest into the Northeast...=20
Days 1-3...

...Significant winter storm to impact large portions of the=20
Northern Plains, Midwest, and Great Lakes through this weekend...

The previous forecast discussion remains very relevant for the
incoming significant winter storm development already materializing
over the Plains and Midwest. Latest UA analysis this afternoon
indicates a positively tilted shortwave trough emerging from the=20
Pacific Northwest, forecast to track southeast into the=20
Northern/Central Plains as we continue through this afternoon. As=20
a secondary vorticity impulses rotates into the trough, this will=20
force downstream amplification of the mid-level pattern, resulting=20
in a negatively tilted trough and increasing ascent downstream into
the Midwest and Great Lakes. At the same time, jet streaks both=20
upstream and downstream of this amplifying trough will begin to=20
couple, producing even more intense deep layer lift, and a surface=20
low will result - first in the lee of the Rockies and then tracking
gradually northeast into MI by Sunday morning. This low will then=20
continue to deepen as it shifts across southeast Canada and exits=20
into the Canadian Maritimes by the end of the forecast period /12Z=20
Monday/.

The guidance this morning has maintained general continuity with=20
better agreement on the track and intensity of this system, and=20
while small temporal and spatial differences among the ensembles=20
still exist, the spread is minimal compared to previous model runs=20
leading to a high confidence scenario in both the expected
evolution and snowfall forecast. As the low deepens and moves=20
northeast, impressive WAA will develop downstream of the developing
cyclone, spreading PWs which will exceed the 90th percentile=20
northward into MO/IA. The accompanying theta-e ridge will surge in=20
tandem and isentropically ascent the region, and while guidance is=20
still not suggesting a strong TROWAL, at least subtle warm air=20
aloft will help develop modest conditional instability. The=20
coincident and impressive 290K isentropic ascent will lead to=20
expanding and intensifying precipitation, with moderate snow likely
across much of the Northern Plains, Upper Midwest, and Great=20
Lakes, especially Friday night through Sunday morning.

On D1, the heaviest snowfall accumulations are likely in a narrow
band driven by the jet streak aloft and the accompanying
ageostrophic/fgen enhancement between 700-600mb. This has allowed
for a stripe of periodically heavy snow over parts of the Dakotas,
spreading into western IA as of the past few hrs. Despite the band=20
being relatively narrow, snowfall rates of 0.5"-1"/hr are likely=20
which could cause 4-6" of snow as reflected by WPC probabilities=20
for 4+ inches that reach above 70%.

However, the most significant part of this event begins later this
evening across IA, spreading eastward through D2 IL/WI/MI. Here,=20
the impressive isentropic ascent will be quite moist as reflected=20
by mixing ratios of 4 g/kg on the 290K surface, leading to a=20
rapidly saturating column. While in general this upglide will=20
result in moderate snowfall rates, there appears to be an=20
increasing risk for heavier snowfall across portions of MO/IA/IL as
the WAA forces an increasing isothermal layer beneath the DGZ=20
which also begins to deepen. Cross-sections are more robust=20
featuring a corridor of folding theta-e surfaces within the=20
elevated RH, suggesting a greater potential for CSI and convective=20
snowfall rates. There is still some uncertainty into this since=20
this signal is much more robust tonight than previous model runs,=20
but locally 1-2"/hr rates appear possible which is supported by the
WPC prototype snowband tool despite a modest overall appearance of
the evolution with respect to conceptual models for heavy snow=20
bands. Still, multiple bands lifting northward for a long duration=20
will result in significant snowfall accumulations and major impacts
for the post- Thanksgiving holiday travel.=20

This will be a significant system with several waves of moderate to
heavy snowfall. On D2, the heaviest accumulations are expected from
far eastern NE through IA, northern IL, and southern WI. WPC
probabilities in this region are 70-100% for more than 6 inches of
snow, and locally as high as 50-70% for more than 12 inches,=20
highest near the Cedar Rapids over into the Quad Cities of IA.=20
Later D2 into D3 the heaviest snow shifts eastward and eventually=20
wanes in intensity, but additional heavy snowfall exceeding 6" is=20
possible, especially around Lake Michigan and into the L.P. of MI.=20
Event total snowfall may reach upwards of 15+" in isolated=20
locations Saturday, potentially setting November and even=20
encroaching some all-time snowfall records for the 24hr and 48hr=20
periods.

Moderate snowfall is also expected across the interior northeast=20
where WPC probabilities D3 are as high as 50-70% for 4+ inches in=20
the higher terrain of VT, NH, and ME.

Key Messages remain in effect for this system (Link #2 below).


...Central Rockies...
Day 3...

No changes necessary to the anticipated evolution of the next
winter disturbance to impact the Central Rockies. A potent=20
shortwave will drop out of the Pacific Northwest Sunday morning,
moving progressively southeast, reaching the Four Corners Sunday=20
night while maintaining a positive tilt. Late D3 this feature will=20
begin to sharpen, with the resulting downstream jet streak=20
intensifying into the Central Plains. The overlap of the RRQ of=20
this jet streak with the greatest height falls ahead of the trough=20
axis will help spawn low pressure in the Great Basin, and this low=20
will help to increase ascent across the Central Rockies Sunday=20
evening. As the overall ascent increases, precipitation will=20
expand, and periods of moderate to heavy snow are likely, generally
above 5000 ft. This system is expected to remain progressive so=20
prolonged snowfall is not expected, but WPC probabilities indicate=20
a moderate risk (50-80% chance) of at least 6 inches of snowfall=20
across the CO Rockies and northern San Juans, with lighter=20
accumulations expected as far west as the Wasatch of Utah.


Weiss/Kleebauer


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!9HzmYz-mIE6DfhJQQBQsOzECv_KFcaoJzdylhJVfCiVsb= -Dbu3RKVB1zEOHkADoLaYbeS0vS7lK--9jlNEGcykLqUmg$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!9HzmYz-mIE6DfhJQQBQsOzECv_KFcaoJzdylhJVfCiVsb= -Dbu3RKVB1zEOHkADoLaYbeS0vS7lK--9jlNEGckf1n8zY$=20



$$

=3D =3D =3D
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FOUS11 KWBC 290825
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
325 AM EST Sat Nov 29 2025

Valid 12Z Sat Nov 29 2025 - 12Z Tue Dec 02 2025


...Northern High Plains through the Midwest into the Northeast...=20
Days 1-2...

...Significant winter storm ramps up across the Midwest today...

A positively tilted shortwave trough diving out of Montana will
sharpen today across the Central Plains, and eventually take on a
negative tilt by this evening in response to secondary vorticity
energy rotating through its base. This evolution will result in
intensifying deep layer ascent in response to more significant
height falls overlapping mid-level divergence, and this will
additionally be aided by increasingly coupled upper jet streaks.
The surface low developing within this impressive ascent will then
deepen as it lifts northeast from Kansas /12Z Saturday/ to Michigan
/12Z Sunday/. This system will become increasingly progressive
through D2, reaching the Canadian Maritimes by 12Z Monday.

This evolution will yield an impressive swath of snow from the
Northern Plains through much of the Midwest and then into the Great
Lakes. As the low develops, increasing warm/moist advection will
surge PWs out of the Gulf, and PW anomalies above the 90th
percentile are progged by NAEFS to reach as far north as MO/IA.
This will occur during a period of intensifying 290K isentropic
ascent, which when occurring beneath the larger scale synoptic lift
will cause snowfall to expand quickly, and become heavy, especially
where 700-600mb fgen intensifies (both due to the WAA and the
ageostrophic response of the upper jet position). At the same time, cross-sections continue to indicate a threat for CSI due to folding
theta-e surfaces, which additionally will support periods of heavy
snowfall rates as laterally translating bands shift northeast
through the region. Snowfall rates of 1-2"/hr are likely (>80%
chance according to the HREF), which, although won't be constant,
will help rapidly accumulate snowfall even with SLRs that will be
around to slightly below climo most of the event.

This intense snowfall will result in widespread significant
impacts, and the WSSI-P indicates a 60-80% chance of major impacts
for parts of IA, IL, and WI, including the Des Moines, Chicago, and
Milwaukee metro areas. This will snarl travel during the busy
post-Thanksgiving holiday weekend. Where snow is the most intense
and longest lasting, record or near-record November snowfall is
possible, especially across eastern IA, southern WI, and northern
IL. This is also where the ECMWF EFI is above 0.9 with an SoT of
1-5, further indicating the potentially record-breaking November
snowfall.

WPC probabilities D1 are high (>70%) for at least 6" of snow from=20
central IA though southern MI, with locally more than 12" possible
(10-30% chance) in eastern IA, southern WI, and northern IL.
Isolated higher totals are possible as well where any banding can
persist due to local convergent features such as indicated by many
of the high-res models near Lake Michigan.

The most significant snowfall should wane quickly from west to east
by 12Z Sunday, but post-system NW flow will create some modest lake
effect snow (LES) across the U.P. and L.P. of MI, as well as east
of Lakes Erie and Ontario Sunday night. Additionally, some modest warm-advection snowfall is likely across the higher terrain of the
interior Northeast before snowfall comes to an end by 12Z Monday.
Additionally snowfall of more than 4 inches is likely (50-90%
chance) according to WPC probabilities from the Chautauqua Ridge
northeast through the higher terrain of the Adirondacks, and into
VT/NH/ME.

Key Messages remain in effect for this system (Key Message 2=20
below).


...Central Rockies through the Mid-Mississippi Valley...=20
Days 2-3...

The next system follows quickly behind the powerful storm across
the Midwest as progressive flow dominates the CONUS.

This system begins as a positively tilted shortwave emerging from
the Pacific Northwest and then digging rapidly into the Four
Corners states by 12Z Monday. As this impulse dives southeast, the
associated vorticity lobe will swing rapidly east, forcing the
evolution into a neutral tilt over the Central/Southern Plains D3,
and potentially becoming negatively tilted late in the forecast
period across the Mid-Mississippi Valley. During this evolution, a
downstream upper jet streak will amplify and pivot poleward over
the Central Plains to enhance deep layer lift. This should cause an
area of heavy snowfall D2 across the Central Rockies, including=20
the Wasatch, Uintas, and CO Rockies where snow levels of around
4000-5000 ft are expected. Although the system is progressive, PW
anomalies above the 90th percentile will support periods of heavy
snow, aided by upslope into the terrain, and WPC probabilities for
more than 4 inches of snow have increased to 70-90% across the Ruby
Mountains in NV, as well as the expanse of the Wasatch, Uintas, CO
Rockies, and San Juans. Locally as much as 12" of snow is possible
in the highest terrain of Colorado.

The forecast becomes more challenging into D3 as this system=20
pushes east. Although the surface wave is likely to wane across the Southern/Central Plains, the downstream impressive jet streak and=20
height falls invof the upper trough will persist. Late Monday, some
of the guidance indicates that the downstream jet and a secondary=20 sub-tropical jet streak emerging across Mexico will phase, leading=20
to secondary low pressure development across the Mississippi=20
Valley. As this occurs, precipitation will expand from the Gulf=20
Coast through the Mid-Mississippi Valley in response to=20
intensifying moist isentropic ascent along the 290K-300K surfaces.=20
Mixing ratios within this plume are progged at 4-8 g/kg, around the
75th-90th percentile for the date, indicative of the impressive
moisture availability in this system.=20

While there are still important timing, location, and thermal=20
differences among the various global members and their associated=20
ensembles, the trends are for a wetter and colder system which=20
could produce significant snow and mixed precipitation before 12Z=20
Tuesday. The AIFS and ECMWF EFI are both well southeast of the=20
highest NBM probabilities during D3, but the D3/D4 clusters=20
indicate high variability due to timing differences of the trough.=20
Despite this uncertainty, current WPC probabilities for at least 2"
of snow are moderate (30-70% chance) from central Kansas through=20
the western Ohio River Valley, with the potent jet streak aloft=20
helping to produce potential banded snow in this region.=20

Additionally, with warm moist air flooding northward from the Gulf
and a retreating cold high pressure in place, a zone of mixed
precipitation, including freezing rain, is likely from the Ozarks
through the southern Appalachians. There continues to be much
uncertainty in the axis of heaviest ice accretions, but
probabilities for at least some modest ice have come up tonight,
leading to increasing confidence in areas of impactful freezing
rain. At this time, WPC probabilities for 0.1" on D3 are as high as
30% in the Ozarks, and 30-50% in the southern Appalachians.

This system will likely continue beyond this forecast period while strengthening, and may create heavy snow across the interior Mid-
Atlantic and Northeast on Tuesday. For this reason, key messages
have been initiated (Key Message 3 below).


Weiss


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!6AjAsWQpkfwy645ER6VQR0wLShDHv63j-1-CD6L3akHfB= DlClvSPq3DonTR_1NKPbrp6WnFzXPoiq9k9rUpb3aiBrZE$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!6AjAsWQpkfwy645ER6VQR0wLShDHv63j-1-CD6L3akHfB= DlClvSPq3DonTR_1NKPbrp6WnFzXPoiq9k9rUpbkFb3CDg$=20



$$

=3D =3D =3D
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FOUS11 KWBC 290829
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
329 AM EST Sat Nov 29 2025

Valid 12Z Sat Nov 29 2025 - 12Z Tue Dec 02 2025


...Northern High Plains through the Midwest into the Northeast...=20
Days 1-2...

...Significant winter storm ramps up across the Midwest today...

A positively tilted shortwave trough diving out of Montana will
sharpen today across the Central Plains, and eventually take on a
negative tilt by this evening in response to secondary vorticity
energy rotating through its base. This evolution will result in
intensifying deep layer ascent in response to more significant
height falls overlapping mid-level divergence, and this will
additionally be aided by increasingly coupled upper jet streaks.
The surface low developing within this impressive ascent will then
deepen as it lifts northeast from Kansas /12Z Saturday/ to Michigan
/12Z Sunday/. This system will become increasingly progressive
through D2, reaching the Canadian Maritimes by 12Z Monday.

This evolution will yield an impressive swath of snow from the
Northern Plains through much of the Midwest and then into the Great
Lakes. As the low develops, increasing warm/moist advection will
surge PWs out of the Gulf, and PW anomalies above the 90th
percentile are progged by NAEFS to reach as far north as MO/IA.
This will occur during a period of intensifying 290K isentropic
ascent, which when occurring beneath the larger scale synoptic lift
will cause snowfall to expand quickly, and become heavy, especially
where 700-600mb fgen intensifies (both due to the WAA and the
ageostrophic response of the upper jet position). At the same time, cross-sections continue to indicate a threat for CSI due to folding
theta-e surfaces, which additionally will support periods of heavy
snowfall rates as laterally translating bands shift northeast
through the region. Snowfall rates of 1-2"/hr are likely (>80%
chance according to the HREF), which, although won't be constant,
will help rapidly accumulate snowfall even with SLRs that will be
around to slightly below climo most of the event.

This intense snowfall will result in widespread significant
impacts, and the WSSI-P indicates a 60-80% chance of major impacts
for parts of IA, IL, and WI, including the Des Moines, Chicago, and
Milwaukee metro areas. This will snarl travel during the busy
post-Thanksgiving holiday weekend. Where snow is the most intense
and longest lasting, record or near-record November snowfall is
possible, especially across eastern IA, southern WI, and northern
IL. This is also where the ECMWF EFI is above 0.9 with an SoT of
1-5, further indicating the potentially record-breaking November
snowfall.

WPC probabilities D1 are high (>70%) for at least 6" of snow from=20
central IA though southern MI, with locally more than 12" possible
(10-30% chance) in eastern IA, southern WI, and northern IL.
Isolated higher totals are possible as well where any banding can
persist due to local convergent features such as indicated by many
of the high-res models near Lake Michigan.

The most significant snowfall should wane quickly from west to east
by 12Z Sunday, but post-system NW flow will create some modest lake
effect snow (LES) across the U.P. and L.P. of MI, as well as east
of Lakes Erie and Ontario Sunday night. Additionally, some modest warm-advection snowfall is likely across the higher terrain of the
interior Northeast before snowfall comes to an end by 12Z Monday.
Additionally snowfall of more than 4 inches is likely (50-90%
chance) according to WPC probabilities from the Chautauqua Ridge
northeast through the higher terrain of the Adirondacks, and into
VT/NH/ME.

Key Messages remain in effect for this system (Key Message 2=20
below).


...Central Rockies through the Ohio Valley...=20
Days 2-3...

The next system follows quickly behind the powerful storm across
the Midwest as progressive flow dominates the CONUS.

This system begins as a positively tilted shortwave emerging from
the Pacific Northwest and then digging rapidly into the Four
Corners states by 12Z Monday. As this impulse dives southeast, the
associated vorticity lobe will swing rapidly east, forcing the
evolution into a neutral tilt over the Central/Southern Plains D3,
and potentially becoming negatively tilted late in the forecast
period across the Mid-Mississippi Valley. During this evolution, a
downstream upper jet streak will amplify and pivot poleward over
the Central Plains to enhance deep layer lift. This should cause an
area of heavy snowfall D2 across the Central Rockies, including=20
the Wasatch, Uintas, and CO Rockies where snow levels of around
4000-5000 ft are expected. Although the system is progressive, PW
anomalies above the 90th percentile will support periods of heavy
snow, aided by upslope into the terrain, and WPC probabilities for
more than 4 inches of snow have increased to 70-90% across the Ruby
Mountains in NV, as well as the expanse of the Wasatch, Uintas, CO
Rockies, and San Juans. Locally as much as 12" of snow is possible
in the highest terrain of Colorado.

The forecast becomes more challenging into D3 as this system=20
pushes east. Although the surface wave is likely to wane across the Southern/Central Plains, the downstream impressive jet streak and=20
height falls invof the upper trough will persist. Late Monday, some
of the guidance indicates that the downstream jet and a secondary=20 sub-tropical jet streak emerging across Mexico will phase, leading=20
to secondary low pressure development across the Mississippi=20
Valley. As this occurs, precipitation will expand from the Gulf=20
Coast through the Mid-Mississippi Valley in response to=20
intensifying moist isentropic ascent along the 290K-300K surfaces.=20
Mixing ratios within this plume are progged at 4-8 g/kg, around the
75th-90th percentile for the date, indicative of the impressive
moisture availability in this system.=20

While there are still important timing, location, and thermal=20
differences among the various global members and their associated=20
ensembles, the trends are for a wetter and colder system which=20
could produce significant snow and mixed precipitation before 12Z=20
Tuesday. The AIFS and ECMWF EFI are both well southeast of the=20
highest NBM probabilities during D3, but the D3/D4 clusters=20
indicate high variability due to timing differences of the trough.=20
Despite this uncertainty, current WPC probabilities for at least 2"
of snow are moderate (30-70% chance) from central Kansas through=20
the western Ohio River Valley, with the potent jet streak aloft=20
helping to produce potential banded snow in this region.=20

Additionally, with warm moist air flooding northward from the Gulf
and a retreating cold high pressure in place, a zone of mixed
precipitation, including freezing rain, is likely from the Ozarks
through the southern Appalachians. There continues to be much
uncertainty in the axis of heaviest ice accretions, but
probabilities for at least some modest ice have come up tonight,
leading to increasing confidence in areas of impactful freezing
rain. At this time, WPC probabilities for 0.1" on D3 are as high as
30% in the Ozarks, and 30-50% in the southern Appalachians.

This system will likely continue beyond this forecast period while strengthening, and may create heavy snow across the interior Mid-
Atlantic and Northeast on Tuesday. For this reason, key messages
have been initiated (Key Message 3 below).


Weiss



...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!9tHzHRjIkt5Wlu4_tiXy9Sv1ZC2dufc5i37Fx8TxUhNW7= OiJVNq0TjnWroPuqfJkGLQTip36UtlIlRHH1vKCqFKDIUk$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!9tHzHRjIkt5Wlu4_tiXy9Sv1ZC2dufc5i37Fx8TxUhNW7= OiJVNq0TjnWroPuqfJkGLQTip36UtlIlRHH1vKCQsKH6jU$=20



$$

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FOUS11 KWBC 292024
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
324 PM EST Sat Nov 29 2025

Valid 00Z Sun Nov 30 2025 - 00Z Wed Dec 03 2025


...Northern High Plains through the Midwest into the Northeast...=20
Days 1-2...

...Significant winter storm unfolding across the Midwest today...

A pair of 500mb vorticity maximums are interacting with one another
and helping to carve out a negatively-tilted 250-500mb layer trough
over the Midwest this afternoon. A coupled 250mb jet streak setup
is further strengthening the ongoing storm system at the surface,
while at the same time, strong 850-700mb WAA ahead of the storm is
promoting 290K isentropic glide over the Midwest that is fostering
highly saturated profiles within a mesoscale environment that is
ripe for heavy snow bands. ECMWF ensembles show S-SWrly 850mb winds
in excess of 60 kts over the Middle MS Valley, which are topping=20
the 99.5 climatological percentile for late Nov and early Dec. This
exceptional LLJ is feeding a slug of 850-500mb moisture northward=20
that will wrap around the storm system and sufficiently saturate=20
the DGZ over the Midwest. WPC's Snowband Probability Tracker, which
utilizes HREF members, shows a band of 1-2"/hr snowfall rates from
central IA today that heads east across the MS River and towards=20
the Great Lakes this evening.=20

Snow will persist throughout the Great Lakes tonight with snow=20
arriving over the Northeast and central Appalachians Sunday=20
morning. LES bands will develop within broad cyclonic flow off=20
Lakes Superior and Michigan and continue through Sunday evening.
LES bands will stick around a little longer downwind of Lakes Erie
and Ontario but eventually taper off by Monday morning as high
pressure moves in. Locally heavy snowfall is possible in parts of=20
the Tug Hill on Sunday, as well as the White Mountains above
2,000ft where steady SWrly upslope flow within an atmosphere
remaining sub-freezing.=20

WPC probabilities depict moderate-to-hgih chances (50-80%) for
additional snowfall totals >6" along and east of the MS River from
eastern IA and southern MN to the Mitten of Michigan. There are
some low chance probabilities (10-30%) for snowfall totals
exceeding 12" in coastal areas of southeast WI, the Chicagoland
metro area, southwest MI, and northern IN where LES bands may
contribute enough snowfall to where over a foot of snow has
accumulated by the time the LES machine concludes. Downwind of Lake
Erie, parts of the Chautauqua Ridge have moderate chances (40-60%)
for snowfall totals >4" through Monday Sunday night. In the
Northeast, the Tug Hill and White Mountains sport moderate-to-high
chances (50-80%) for snowfall accumulations >6" with localized=20
totals approaching 12" possible by the time this winter storm=20
concludes. The WSSI continues to summarize this storm well,=20
highlighting Moderate to locally Major impacts from central IA on=20
east through the Milwaukee/Chicago metro areas and into northern IN
and southern MI. Expect considerable disruptions to travel in=20
these areas as travelers are likely to encounter numerous travels=20
delays by both road and by air today and lingering through tonight.

Key Messages remain in effect for this system (Key Message 2=20
below).


...Central Rockies through the Ohio Valley, Ice in the Ozarks...=20
Days 2-3...

A positively titled 500mb trough diving south from the Northwest
into the Central Rockies on Sunday will contain both sufficient
synoptic-scale lift and 700-300mb mean layer moisture to support
rounds of mountain snow from central OR and the northern Great
Basin on east across the Wasatch and into the CO Rockies. The
heavier totals in the Great Basin and Wasatch will generally=20
reside above 8,000ft, while the CO/northern NM Rockies are most=20
likely to see their heavier snowfall totals above 9,000ft. WPC=20
probabilities show these listed elevations as having >50% chances=20
for snowfall >8" with localized totals >12" in the peaks of the CO=20 Rockies.=20

As snow continues across the Central Rockies Sunday night, the
aforementioned 500mb trough will begin to eject east into the
Central Plains. A strengthening surge in 700mb WAA and the 500mb=20
PVA will foster a blossoming area of snowfall from the central
Plains to the Middle MS Valley. Snowfall totals are most likely to
range between a coating-3", although WPC probabilities do show low
chances (10-30%) for snowfall totals >4" over northeast KS,
southeast NE, and northern MO through Monday morning. This narrow=20
plume of snow races east across the Lower Great Lakes and OH Valley
Monday evening with similar snowfall totals.

Farther south, as low-level WAA and moisture over-run an air-mass
that features sub-freezing temperatures and dry dew points, a setup
for freezing rain unfolds from the ArkLaTex on across much of AR,
northern MS, western TN, and southern MO. The plume of low-level
moisture does not last too long, but 290K isentropic ascent sticks
around long enough for some disruptive ice accumulations in parts
of these areas on Monday. WPC probabilities show low chances
(10-30%) for ice accumulations over a tenth of and inch, but there
are moderate chances (40-60%) for at least a hundredth of an inch.
The WSSI-P does show up to 40% odds for Minor Impacts as a result
of this freezing rain setup on Monday across much of central AR.=20


...Central Appalachians, Mid-Atlantic, & Northeast...
Day 3-3.5...

...A complex & potentially disruptive winter storm to affect these
regions on Tuesday and into Tuesday night...

Summary: The first accumulating snowfall and disruptive ice event=20
of the season is likely to occur from the Central Appalachians and=20
interior Mid-Atlantic to the Northeast. There remain ongoing=20
changes and disagreements in guidance with snowfall totals, who=20
sees the heaviest totals, and timing all still lower in confidence.
Those in these regions should monitor the forecast from WPC and=20
their local WFOs over the next 24-48 hours.=20

Analysis: As the Central Plains disturbance tracks east Monday=20
evening, there are three other disturbances that are influencing=20
this complicated setup. The first is a weak feature over South TX=20
that is running just out in front of the main upper trough over the
Central Plains. Second: a fast moving 500mb trough over south-=20
central Canada racing southeastward through the Great Lakes by=20
Monday night. Third:the departing system over the Northeast on=20
Monday that races east of Atlantic Canada Monday night. Where=20
guidance is in agreement is that the primary trough over the=20
Central Plains works in tandem with the ejecting Deep South=20
disturbance to direct a plume of 700-300mb moisture at the East=20
Coast. This moisture source will overrun a residual sub-freezing=20
air-mass Monday night over the Central Appalachians and Mid-=20
Atlantic that will support disruptive ice accumulations. However,=20
the dome of high pressure is departing as the storm approaches. For
areas west and north of I-95 in the Mid-Atlantic, boundary layer=20
wet-bulb temperatures will support at least a brief period for=20
accumulating snow. By 18Z Tuesday, a coupling 500mb jet streak=20
setup will support strong vertical ascent aloft that deepens a=20
coastal low as it tracks off the coast. To the north of the storm=20
track, heavy-banded precipitation to the north of a 850-700mb FGEN
band will transpire with snow most likely to occur north of I-95=20
in the higher terrain.

This is where the agreements in the overall setup end. Guidance
members such as the ECMWF show a less amplified Middle MS Valley
feature and less phasing with the Great Lakes disturbance, with
that Great Lakes feature suppressing the storm tracks with its
ensemble membership over the GEFS. Meanwhile, the GEPS are north
and more amplified compared to the GEFS, making the GEFS the
middle ground in storm position. Notably, the EC-AIFS ensemble
means is stronger with the surface low as it reaches the East=20
Coast on Tuesday and its QPF footprint is farther up the coast than
the EPS membership is. At the moment, the ECMWF is on the drier=20
side of guidance, while other like the CMC/NAM are much more=20
amplified. What today's trends have favored, as of this discussion,
is a slightly faster solution that would allow for precipitation=20
to arrive sooner on Tuesday morning.=20

With the cold air-mass retreating on Tuesday, the expectations for
those from northern VA and northern MD on north and east through=20
southeast PA, the Delaware Valley, and into southern New England
was to favor lower SLRs, which should make for a heavy/wet snow.=20
That said, the storm track is critical in determining how far north
the rain/snow line gets. As is the case in marginal boundary layer
temperature environments with fast moving coastal lows that are=20
unable to develop a robust deformation zone, plus baking in=20
climatology for the time of year, it should be the higher=20
elevations north and west of I-95 that are most favored for=20
accumulating snowfall. This setup favors interior New England for=20
heavy snow, although should the Great Lakes disturbance act to=20
suppress the storm track, this could shift farther south to the=20
Catskills and higher terrain of southern New England.=20

WPC probabilities show moderate-to-high chances (50-70%) for=20
snowfall totals >4" from east-central PA on north and east through=20
the Poconos, Catskills, Berkshires, Green, and White Mountains.=20
Farther south, the Philly/Baltimore/DC metro areas may start out=20
briefly as snow, but transition to a wintry mix on Tuesday. There=20
is a possibility for a more icy scenario should cold-air damming=20
(CAD) stick around longer on Tuesday before transitioning to plain
rain. Speaking of CAD, the Central Appalachians will see sub-=20
freezing surface temperatures persist long enough to support a=20
treacherous freezing rain event. WPC probabilities depict=20
moderate-to-high chances (50-80%) for ice accumulations over a=20
tenth of an inch from the Blue Ridge of western NC on north through
the WV/VA Appalachians and Shenandoah Valley with low chances=20
(10-30%) for over a quarter inch of ice. The WSSI-P shows a swath=20
of >50% chances for Minor Impacts from the Central Appalachians on=20
north and east through the WV Panhandle, along and west of Parrs'=20
Ridge in northern MD, through east-central PA, northern NJ, southern
NY, and the interior areas of New England. Key messages are=20
ongoing for this system (Key Message 3 below).=20


Mullinax


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!-II4-v4O3ltIgIqqc2v258ylBcED4sbm6CU-CkNDfY5qL= K4MAm3zknjfJhB255Hjom1Yu-Xc5gaRSOypkDlfvV8Ix70$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!-II4-v4O3ltIgIqqc2v258ylBcED4sbm6CU-CkNDfY5qL= K4MAm3zknjfJhB255Hjom1Yu-Xc5gaRSOypkDlfOJ_EuZY$=20




$$

=3D =3D =3D
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FOUS11 KWBC 292040
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
340 PM EST Sat Nov 29 2025

Valid 00Z Sun Nov 30 2025 - 00Z Wed Dec 03 2025


...Northern High Plains through the Midwest into the Northeast...=20
Days 1-2...

...Significant winter storm unfolding across the Midwest today...

A pair of 500mb vorticity maximums are interacting with one another
and helping to carve out a negatively-tilted 250-500mb layer trough
over the Midwest this afternoon. A coupled 250mb jet streak setup
is further strengthening the ongoing storm system at the surface,
while at the same time, strong 850-700mb WAA ahead of the storm is
promoting 290K isentropic glide over the Midwest that is fostering
highly saturated profiles within a mesoscale environment that is
ripe for heavy snow bands. ECMWF ensembles show S-SWrly 850mb winds
in excess of 60 kts over the Middle MS Valley, which are topping=20
the 99.5 climatological percentile for late Nov and early Dec. This
exceptional LLJ is feeding a slug of 850-500mb moisture northward=20
that will wrap around the storm system and sufficiently saturate=20
the DGZ over the Midwest. WPC's Snowband Probability Tracker, which
utilizes HREF members, shows a band of 1-2"/hr snowfall rates from
central IA today that heads east across the MS River and towards=20
the Great Lakes this evening.=20

Snow will persist throughout the Great Lakes tonight with snow=20
arriving over the Northeast and central Appalachians Sunday=20
morning. LES bands will develop within broad cyclonic flow off=20
Lakes Superior and Michigan and continue through Sunday evening.
LES bands will stick around a little longer downwind of Lakes Erie
and Ontario but eventually taper off by Monday morning as high
pressure moves in. Locally heavy snowfall is possible in parts of=20
the Tug Hill on Sunday, as well as the White Mountains above
2,000ft where steady SWrly upslope flow within an atmosphere
remaining sub-freezing.=20

WPC probabilities depict moderate-to-hgih chances (50-80%) for
additional snowfall totals >6" along and east of the MS River from
eastern IA and southern MN to the Mitten of Michigan. There are
some low chance probabilities (10-30%) for snowfall totals
exceeding 12" in coastal areas of southeast WI, the Chicagoland
metro area, southwest MI, and northern IN where LES bands may
contribute enough snowfall to where over a foot of snow has
accumulated by the time the LES machine concludes. Downwind of Lake
Erie, parts of the Chautauqua Ridge have moderate chances (40-60%)
for snowfall totals >4" through Monday Sunday night. In the
Northeast, the Tug Hill and White Mountains sport moderate-to-high
chances (50-80%) for snowfall accumulations >6" with localized=20
totals approaching 12" possible by the time this winter storm=20
concludes. The WSSI continues to summarize this storm well,=20
highlighting Moderate to locally Major impacts from central IA on=20
east through the Milwaukee/Chicago metro areas and into northern IN
and southern MI. Expect considerable disruptions to travel in=20
these areas as travelers are likely to encounter numerous travels=20
delays by both road and by air today and lingering through tonight.

Key Messages remain in effect for this system (Key Message 2=20
below).


...Central Rockies through the Ohio Valley, Ice in the Ozarks...=20
Days 2-3...

A positively titled 500mb trough diving south from the Northwest
into the Central Rockies on Sunday will contain both sufficient
synoptic-scale lift and 700-300mb mean layer moisture to support
rounds of mountain snow from central OR and the northern Great
Basin on east across the Wasatch and into the CO Rockies. The
heavier totals in the Great Basin and Wasatch will generally=20
reside above 8,000ft, while the CO/northern NM Rockies are most=20
likely to see their heavier snowfall totals above 9,000ft. WPC=20
probabilities show these listed elevations as having >50% chances=20
for snowfall >8" with localized totals >12" in the peaks of the CO=20 Rockies.=20

As snow continues across the Central Rockies Sunday night, the
aforementioned 500mb trough will begin to eject east into the
Central Plains. A strengthening surge in 700mb WAA and the 500mb=20
PVA will foster a blossoming area of snowfall from the central
Plains to the Middle MS Valley. Snowfall totals are most likely to
range between a coating-3", although WPC probabilities do show low
chances (10-30%) for snowfall totals >4" over northeast KS,
southeast NE, and northern MO through Monday morning. This narrow=20
plume of snow races east across the Lower Great Lakes and OH Valley
Monday evening with similar snowfall totals.

Farther south, as low-level WAA and moisture over-run an air-mass
that features sub-freezing temperatures and dry dew points, a setup
for freezing rain unfolds from the ArkLaTex on across much of AR,
northern MS, western TN, and southern MO. The plume of low-level
moisture does not last too long, but 290K isentropic ascent sticks
around long enough for some disruptive ice accumulations in parts
of these areas on Monday. WPC probabilities show low chances
(10-30%) for ice accumulations over a tenth of and inch, but there
are moderate chances (40-60%) for at least a hundredth of an inch.
The WSSI-P does show up to 40% odds for Minor Impacts as a result
of this freezing rain setup on Monday across much of central AR.=20


...Central Appalachians, Mid-Atlantic, & Northeast...
Day 3-3.5...

...A complex & potentially disruptive winter storm to affect these
regions on Tuesday and into Tuesday night...

Summary: The first accumulating snowfall and disruptive ice event=20
of the season is likely to occur from the Central Appalachians and=20
interior Mid-Atlantic to the Northeast. There remain ongoing=20
changes and disagreements in guidance with snowfall totals, who=20
sees the heaviest totals, and timing all still lower in confidence.
Those in these regions should monitor the forecast from WPC and=20
their local WFOs over the next 24-48 hours.=20

Analysis: As the Central Plains disturbance tracks east Monday=20
evening, there are three other disturbances that are influencing=20
this complicated setup. The first is a weak feature over South TX=20
that is running just out in front of the main upper trough over the
Central Plains. Second: a fast moving 500mb trough over south-=20
central Canada racing southeastward through the Great Lakes by=20
Monday night. Third:the departing system over the Northeast on=20
Monday that races east of Atlantic Canada Monday night. Where=20
guidance is in agreement is that the primary trough over the=20
Central Plains works in tandem with the ejecting Deep South=20
disturbance to direct a plume of 700-300mb moisture at the East=20
Coast. This moisture source will overrun a residual sub-freezing=20
air-mass Monday night over the Central Appalachians and Mid-=20
Atlantic that will support disruptive ice accumulations. However,=20
the dome of high pressure is departing as the storm approaches. For
areas west and north of I-95 in the Mid-Atlantic, boundary layer=20
wet-bulb temperatures will support at least a brief period for=20
accumulating snow. By 18Z Tuesday, a coupling 500mb jet streak=20
setup will support strong vertical ascent aloft that deepens a=20
coastal low as it tracks off the coast. To the north of the storm=20
track, heavy-banded precipitation to the north of a 850-700mb FGEN
band will transpire with snow most likely to occur north of I-95=20
in the higher terrain.

This is where the agreements in the overall setup end. Guidance
members such as the ECMWF show a less amplified Middle MS Valley
feature and less phasing with the Great Lakes disturbance, with
that Great Lakes feature suppressing the storm tracks with its
ensemble membership over the GEFS. Meanwhile, the GEPS are north
and more amplified compared to the GEFS, making the GEFS the
middle ground in storm position. Notably, the EC-AIFS ensemble
means is stronger with the surface low as it reaches the East=20
Coast on Tuesday and its QPF footprint is farther up the coast than
the EPS membership is. At the moment, the ECMWF is on the drier=20
side of guidance, while other like the CMC/NAM are much more=20
amplified. What today's trends have favored, as of this discussion,
is a slightly faster solution that would allow for precipitation=20
to arrive sooner on Tuesday morning.=20

With the cold air-mass retreating on Tuesday, the expectations for
those from northern VA and northern MD on north and east through=20
southeast PA, the Delaware Valley, and into southern New England
was to favor lower SLRs, which should make for a heavy/wet snow.=20
That said, the storm track is critical in determining how far north
the rain/snow line gets. As is the case in marginal boundary layer
temperature environments with fast moving coastal lows that are=20
unable to develop a robust deformation zone, plus baking in=20
climatology for the time of year, it should be the higher=20
elevations north and west of I-95 that are most favored for=20
accumulating snowfall. This setup favors interior New England for=20
heavy snow, although should the Great Lakes disturbance act to=20
suppress the storm track, this could shift farther south to the=20
Catskills and higher terrain of southern New England.=20

WPC probabilities show moderate-to-high chances (50-70%) for=20
snowfall totals >4" from east-central PA on north and east through=20
the Poconos, Catskills, Berkshires, Green, and White Mountains.=20
Farther south, the Philly/Baltimore/DC metro areas may start out=20
briefly as snow, but transition to a wintry mix on Tuesday. There=20
is a possibility for a more icy scenario should cold-air damming=20
(CAD) stick around longer on Tuesday before transitioning to plain
rain. Speaking of CAD, the Central Appalachians will see sub-=20
freezing surface temperatures persist long enough to support a=20
treacherous freezing rain event. WPC probabilities depict=20
moderate-to-high chances (50-80%) for ice accumulations over a=20
tenth of an inch from the Blue Ridge of western NC on north through
the WV/VA Appalachians and Shenandoah Valley with low chances=20
(10-30%) for over a quarter inch of ice. The WSSI-P shows a swath=20
of >50% chances for Minor Impacts from the Central Appalachians on=20
north and east through the WV Panhandle, along and west of Parrs'=20
Ridge in northern MD, through east-central PA, northern NJ,
southern NY, and interior New England. Key messages are ongoing=20
for this system (Key Message 3 below).=20


Mullinax



...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_2.png__;!!DZ3fjg!_sInBjlekP6pjNLeRE9LcvsU1nax_MbMvx1zivFGkr4Rq= k-U2PID8H1T0KDpJqo1tgG6WZCgot_ZewEEuM12DI18XNw$=20

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!_sInBjlekP6pjNLeRE9LcvsU1nax_MbMvx1zivFGkr4Rq= k-U2PID8H1T0KDpJqo1tgG6WZCgot_ZewEEuM12uPpTWiE$=20



$$

=3D =3D =3D
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FOUS11 KWBC 300739
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
239 AM EST Sun Nov 30 2025

Valid 12Z Sun Nov 30 2025 - 12Z Wed Dec 03 2025


...Great Lakes to the Interior Northeast...
Day 1...

The major winter storm plaguing the Upper Midwest will wane as the
parent shortwave de-amplifies into a positive tilt and becomes more
embedded in the westerlies across Canada. This will cause a more
rapid progression of the driving low pressure, leading to moderate
continued snow accumulations across the Great Lakes, and expanding
across the higher terrain of the interior Northeast.

The surface low is progged to track from the L.P. of Michigan this
morning into the Canadian Maritimes by Monday morning /end of D1/.
This will result in two areas of additional snowfall accumulation.=20

The first is expected across the Great Lakes as NW flow develops in
the wake of the surface low. While brief deformation snow is likely
as the low departs Michigan, most of the additional snowfall is
likely to be of the lake effect snow (LES) variety as CAA
strengthens across the lakes. 850mb temps falling to -10C or lower
will support steep lapse rates and inversion depths rising to
around 800mb to support at least a brief period of heavy LES with
rates exceeding 1"/hr (40-60% chance from the HREF). The most
likely belts of heavy LES D1 will be across the eastern U.P., the
northern L.P., SW MI, and then east of Lake Ontario. In these
areas, WPC probabilities are 50-70% for more than 4 inches, with=20
locally as much as 8 inches east of Lake Ontario.

The other area of heavy snow from this system will be across the
higher terrain of Upstate NY and Northern New England. WAA
expanding northward downstream of the surface low will spread into
Canada, drawing a narrow column of moisture from the Gulf to cause
expanding precipitation in New England. The WAA is impressive but
transient, and regional forecast soundings suggest persistent mid-
level dry air which will somewhat preclude precipitation rate
intensity. Additionally, the cold high pressure over the region
early will rapidly retreat east, leading to funneled southerly=20
flow with no cold air entrenchment. This suggests that the heaviest
snow will be confined only to the higher terrain of the=20
Adirondacks, Greens, and Whites, where WPC probabilities are=20
moderate (30-50%) for 4+ inches of snowfall.


...Central Rockies/Four Corners...
Days 1-2...

A closed 500mb low dropping out of the Interior Northwest will move progressively southeast today while opening into a positively
tilted trough. The base of this feature will reach the Four Corners
Monday morning before continuing to eject into the Central Plains,
and the overlap of height falls with an amplifying jet streak will
produce large scale ascent across the Central Rockies and Four
Corners today. Available moisture is somewhat scarce (PWs only
around 0.25" and around the 10th percentile according to NAEFS) but
the impressive, albeit transient, deep layer lift will overcome
that to produce a swath of heavy snowfall. Snow should begin across
the Great Basin this morning, but intensify in response to better
lift aided by upslope flow over the Wasatch/Uintas this afternoon,
and then the CO Rockies/San Juans/Sangre de Cristos this evening
and tonight. Snow should end early Monday morning. WPC=20
probabilities suggest a high risk (>80% chance) of more than 6=20
inches across most of these mountain ranges, with snow levels=20
generally 4000-5000 ft.



...Central Plains & Ozarks through the Northeast...
Days 2-3...

...Widespread impactful snow and ice likely, but uncertainty with
respect to timing and track remains...

A complex evolution of mid-level features will create the first
widespread winter precipitation event from the Ohio Valley into the Appalachians, Mid-Atlantic, and Northeast. However, uncertainty
remains considerable at this time range and model guidance
continues to feature a variety of solutions which will affect the
accompanying impacts.

This system will develop initially in response to a shortwave
diving out of the Central Rockies Monday afternoon, and this
feature is expected to become neutrally tilted as vorticity lobes
swing through its base by the time it reaches the Ohio Valley
Tuesday morning. Thereafter, the shortwave tracks rapidly east
while maintaining its modest amplitude, exiting New England by 12Z
Wednesday. The global guidance has come into much better agreement
this morning with the progged evolution, maintaining a flatter and
faster wave, and in general, this upper pattern does not=20
conceptually support a widespread significant snowfall.=20

However, there are caveats that may make this a bit more=20
impressive than it would otherwise appear at 500mb. This is=20
primarily due to the amplification and phasing of upper jet=20
streaks: one amplifying downstream of the shortwave and a second=20
subtropical jet streak emerging from Mexico. The interaction of
this jet energy is progged to occur across the Mid-Mississippi
Valley Monday night, with the strengthening result then arcing
poleward through Tuesday to provide more impressive lift both
through the RRQ and LFQ. The strengthening jet streak will provide
sufficient upper ventilation, in conjunction with the mid-level
height falls, to produce surface cyclogenesis along the Gulf Coast
Tuesday morning, with this low then deepening as it tracks rapidly
northeast to off the coast of the Carolinas and then towards the
40/70N benchmark. The SLP trends of the various ensemble camps=20
have been for a faster solution with also some latitudinal gain,=20
suggesting this will not be a heavy snow event for the I-95=20
corridor, which is supported by an unfavorable surface high=20
position as well, but could still cause impactful wintry=20
precipitation across a large area.

As the synoptics intensify and the surface low moves east,
increasing WAA on a 30-50 kts 850mb LLJ will spread northward
leading to an expansion of precipitation. Where this interacts with
the strengthening jet streak, a stripe of heavy banded
precipitation is likely, which will fall as snow in many areas.=20

The first band is expected Monday into Monday night from the=20
Central Plains through the Ohio Valley where the ageostrophic=20
response to the LFQ of the upper jet will help intensify 700-600mb=20
fgen, crossing directly the deepening DGZ (SREF DGZ 50mb depth=20
probabilities > 50%). This should produce a stripe of heavy snow
rates from KS through the Ohio Valley, and although the band will
be progressive, WPC probabilities indicate a moderate risk (50-70%
chance) for at least 2 inches from central KS through eastern OH,
with locally higher amounts of 4+ inches possible (10-30%) aided by
fluffy SLRs. South of this band, increasing moist isentropic=20
ascent atop the retreating cold air will result in an axis of=20
freezing rain across the Ozarks where WPC probabilities are modest
(10-30%) for at least 0.1" of ice accretion, highest in central AR.

Then, during D3 /12Z Tue to 12Z Wed/ the moist isentropic ascent
maximizes leading to widespread heavy precipitation along and ahead
of the strengthening low pressure system. With the surface high
retreating and a lack of mid-level confluence to lock in cold air,
many areas of the Mid-Atlantic into the Northeast will begin as a
brief period of mixed precip, but should quickly change to rain
Tuesday morning, especially along and east of I-95. Inland,
however, the strong WAA, especially in the 850-700mb layer, will=20
result in front end heavy snow, most likely from Kentucky northeast
into interior New England. There is still uncertainty into how far
north the warm air will spread to cause changeover, but=20
significant snow accumulations are likely as reflected by WPC
probabilities that have increased, and now suggest a greater than
70% chance for 4+ inches of snow from the Poconos through Downeast
Maine. Locally more than 8 inches is possible, most likely in the
higher terrain of central New England. It is prudent to note that=20
while most of the guidance does not support an I-95 snow event, the
ECMWF AIFS ensemble, and even to some degree the EFI, suggest some
heavier snow farther south than most of the other camps, which=20
could bring more impactful weather to I-95 and is worth continuing=20
to monitor.

Finally, south of the heavy snow and across the terrain of the
Southern and Central Appalachians, a period of light to moderate
freezing rain is likely which could cause impactful ice
accretions, especially in the higher terrain. Current WPC
probabilities are as high as 30-50% for 0.1" of ice, with local
amounts approaching 0.25" possible in the vicinity of the Blue
Ridge of NC and VA.

Key Messages remain in effect for this system and are linked below
(Key Message #3)


Weiss


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!_c96Fsm1kuyRpsYRqexGYrwZpDlGi30W0sU9cwbGm13v6= 4qFD27sEGEjMb_FSIQmd90IuTeJ7bqYRbSGk1Vc1yHTKf4$=20



$$

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FOUS11 KWBC 302021
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
321 PM EST Sun Nov 30 2025

Valid 00Z Mon Dec 01 2025 - 00Z Thu Dec 04 2025


...Great Lakes to the Interior Northeast...
Day 1...

The storm system responsible for the heavy and disruptive snowfall
that blanketed the Midwest and Great Lakes is tracking into Ontario
this afternoon. Cyclonic flow and CAA within WNW-NW winds will
reinvigorate the LES machine across the Upper Great Lakes, snow
belts of western MI and northern IN, and typical snow belts to the
east of Lakes Erie and Ontario. Snow bands will be capable of
producing anywhere between 1-2"/hr snowfall rates due to the
favorably unstable low-level profiles and a pivoting 850-700mb
trough over head this evening. WPC probabilities show moderate
chance probabilities (40-60%) for additional snowfall totals >4"=20
over far northwest PA and across the Tug Hill. An additional 1-4"
of snow is forecast in the Green and White Mountains before
tapering off by early Monday morning.


...Central Rockies/Central Plains/Mid-South/OH Valley...
Days 1-2...

A 500mb positiviely-tilted trough is tracking through UT today and
will head for the CO/NM Rockies by early Monday morning. The
combination of height falls with a strengthening jet streak will=20
produce large scale ascent across the Central Rockies and Four=20
Corners today and into tonight. Heavy snowfall will be primarily
confined to the >10,000ft peaks of the CO/NM Rockies, although some minor-to-moderate accumulations between 7,000-10,000ft are
possible.=20

As the upper trough tracks east towards the Central Plains tonight,
healthy 500mb PVA coupled with a strengthening 250mb jet streak
will foster healthy synoptic-scale divergence aloft. Guidance also
shows a strengthening 850-700mb WAA regime and corresponding 290K
isentropic ascent over the Central Plains that is likely to result
in a band of moderate-to-heavy snow tracking from northern KS early
Monday morning and across the heart of the Midwest by Monday
afternoon. Temperatures are cold enough aloft to support fluffy
SLRs (>15:1 in most cases) and it is progressive. WPC probabilities
show most accumulations will range between 1-4", given WPC
probabilities for >4" are low (10-30% at most in northeast
KS/northwest MO). However, there are some guidance members that
depict some localized totals >4" by the time the band of snow exits
to the east Monday evening. The same mechanism producing snow in=20
the Central Plains heads for the OH Valley and western PA. Snowfall accumulations will generally range between 1-4" through Tuesday=20
morning.=20

Farther south, as low-level WAA and Gulf moisture spreads over and
air-mass that features sub-freezing temperatures and dry
dewpoints, freezing rain is expected to unfold from the
ArkLaTex eastward across central and southern AR and into western
TN. the plume of low-level moisture does not last long, but 290K
isentropic ascent sticks around long enough for some disruptive=20
ice accumulations in these areas on Monday. WPC probabilities show=20
low chances (10-30%) for ice accumulations than one-tenth of an=20
inch, but there are moderate chances (40-60%) for ice=20
accumulations over one-hundreth in central AR. The WSSI shows a=20
large swath of Minor Impacts across central AR and as far north as=20
the MO/AR border, but some localized Moderate Impacts in central AR
are possible.=20


...Central Appalachians & Northeast...
Days 2-3...

...Widespread hazardous snow and ice to blanket portions of the
Mid-Atlantic and Northeast Monday night and through Tuesday...

By Monday evening, the 500mb trough producing periods of snow over
the OH Valley will track across the Middle MS Valley Monday night
with a secondary disturbance tracking south of it towards the
Southeast. As a third disturbance approaches from the Great Lakes,
a strengthening 250mb jet streak over the Northeast will work with
a second 250mb jet streak over the South to creating a classic
"coupling jet streak" setup off the Mid-Atlantic coast. This will
be the basis for a strengthening winter storm that tracks initially
through the Southeast Monday night and up the East Coast by Tuesday
afternoon.

The primary ingredients are generally agreed upon on all guidance,
although how they come together and where the storm tracks is=20
still coming into focus. High pressure over the Northeast will=20
initially provide a sufficiently cold air-mass to support wintry=20 precipitation at the onset from the Central Appalachians on north=20
and east, but it will be exiting off Atlantic Canada on Tuesday. As
925-700mb WAA advances north Monday night and into Tuesday, any=20
initial snow over the Central Appalachians will changeover to a=20 sleet/freezing rain mix, then all freezing rain. Cold air damming=20
(CAD) will linger long enough in the higher terrain to support=20
disruptive ice accumulations that result in slick travel conditions
Monday night and into Tuesday morning. WPC probabilities show >50%
chances for ice accumulations over a tenth of an inch from the=20
Blue Ridge of western NC on north through the mountains of western=20
VA and eastern WV. There are some low-chance probabilities (10-30%)
for over a quarter inch of ice from VA's Skyline Drive on south and west
to the WV/VA border. The latest WSSI does depict Minor to Moderate
Impacts in these regions with a focus on treacherous travel=20
conditions.

Farther north over the Mid-Atlantic, precipitation is likely to
start out as snow over northern VA/MD, southern PA, and on north
towards the NYC metro Tuesday morning. Guidance then begins to
disagree on the handling of the transition and northward expansion
of the snow-wintry mix area. Low-level SErly flow is strong enough
to where most areas along I-95 should flip over to plain rain on
Thursday morning, but farther inland over the Piedmont of VA,
northern MD, and Lower Susquehanna Valley, low-lvel cold may stick
around long enough for a wintry mix to hang around longer. This is
likely to be the region's first accumulating snowfall, so there are
likely to detrimental impacts to travel even if snowfall and ice
accumulations are minor (1-3" of snow for these areas, up to a=20
tenth of an inch of ice in western MD and northwest VA). However,=20
from the Lehigh Valley and Poconos on north and east through=20
northwest NJ, the Catskills, and into interior southern New=20
England, snow is likely to remain the primary precip type.

The storm by Tuesday afternoon will begin to develop a closed lower
over the Delaware Valley that deepens south of Long Island by
Tuesday evening. To the north and east of the 850mb low, a
consolidated 850-700mb FGEN area will develop and result in a band
of heavy snow somewhere from northeast PA and southern NY (north of
NYC) through southern New England. Snowfall rates within this band
are likely to at least top 1"/hr. There still remains some
uncertainty on where this band sets up, but probabilistic guidance
is showing increase odds on a snowfall swath of >6" from the
Poconos and Catskills on north and east. The higher terrain across
New England (Berkshires, Worcester Hills, Green, Whites, Downeast
Maine) are the most favored for locally heavy snowfall as WPC=20
probabilities shows low-to-moderate chances (30-50%) for over 12"=20
in some spots. The latest WSSI does depict Moderate Impacts due to
snow from western MA and northern CT to southern NH and southern=20
ME with locally Major Impacts possible.=20

In summary, this is going to be the first accumulating snow of the
season for many areas from southern PA to areas just west of I-95,
potentially including the Boston metro area should more southern
guidance come to fruition. Expect travel delays on Tuesday and into
Tuesday night in affected areas. High pressure and dry conditions
return to the Northeast by early Wednesday morning.=20

Key Messages remain in effect for this system and are linked below
(Key Message #3)


Mullinax


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!8j1a6fpP7PIestX6LxHG47zf9CWUftnDL_uYhqq5y-hZB= QnAJRuMy4jSvIskYFi6EXdf5gXbLAYOTj_7E-hkDpvbjsY$=20



$$

=3D =3D =3D
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FOUS11 KWBC 302029
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
329 PM EST Sun Nov 30 2025

Valid 00Z Mon Dec 01 2025 - 00Z Thu Dec 04 2025


...Great Lakes to the Interior Northeast...
Day 1...

The storm system responsible for the heavy and disruptive snowfall
that blanketed the Midwest and Great Lakes is tracking into Ontario
this afternoon. Cyclonic flow and CAA within WNW-NW winds will
reinvigorate the LES machine across the Upper Great Lakes, snow
belts of western MI and northern IN, and typical snow belts to the
east of Lakes Erie and Ontario. Snow bands will be capable of
producing anywhere between 1-2"/hr snowfall rates due to the
favorably unstable low-level profiles and a pivoting 850-700mb
trough over head this evening. WPC probabilities show moderate
chance probabilities (40-60%) for additional snowfall totals >4"=20
over far northwest PA and across the Tug Hill. An additional 1-4"
of snow is forecast in the Green and White Mountains before
tapering off by early Monday morning.


...Central Rockies/Central Plains/Mid-South/OH Valley...
Days 1-2...

A 500mb positiviely-tilted trough is tracking through UT today and
will head for the CO/NM Rockies by early Monday morning. The
combination of height falls with a strengthening jet streak will=20
produce large scale ascent across the Central Rockies and Four=20
Corners today and into tonight. Heavy snowfall will be primarily
confined to the >10,000ft peaks of the CO/NM Rockies, although some minor-to-moderate accumulations between 7,000-10,000ft are
possible.=20

As the upper trough tracks east towards the Central Plains tonight,
healthy 500mb PVA coupled with a strengthening 250mb jet streak
will foster healthy synoptic-scale divergence aloft. Guidance also
shows a strengthening 850-700mb WAA regime and corresponding 290K
isentropic ascent over the Central Plains that is likely to result
in a band of moderate-to-heavy snow tracking from northern KS early
Monday morning and across the heart of the Midwest by Monday
afternoon. Temperatures are cold enough aloft to support fluffy
SLRs (>15:1 in most cases) and it is progressive. WPC probabilities
show most accumulations will range between 1-4", given WPC
probabilities for >4" are low (10-30% at most in northeast
KS/northwest MO). However, there are some guidance members that
depict some localized totals >4" by the time the band of snow exits
to the east Monday evening. The same mechanism producing snow in=20
the Central Plains heads for the OH Valley and western PA. Snowfall accumulations will generally range between 1-4" through Tuesday=20
morning.=20

Farther south, as low-level WAA and Gulf moisture spreads over and
air-mass that features sub-freezing temperatures and dry
dewpoints, freezing rain is expected to unfold from the
ArkLaTex eastward across central and southern AR and into western
TN. the plume of low-level moisture does not last long, but 290K
isentropic ascent sticks around long enough for some disruptive=20
ice accumulations in these areas on Monday. WPC probabilities show=20
low chances (10-30%) for ice accumulations than one-tenth of an=20
inch, but there are moderate chances (40-60%) for ice=20
accumulations over one-hundreth in central AR. The WSSI shows a=20
large swath of Minor Impacts across central AR and as far north as=20
the MO/AR border, but some localized Moderate Impacts in central AR
are possible.=20


...Central Appalachians & Northeast...
Days 2-3...

...Widespread hazardous snow and ice to blanket portions of the
Mid-Atlantic and Northeast Monday night and through Tuesday...

By Monday evening, the 500mb trough producing periods of snow over
the OH Valley will track across the Middle MS Valley Monday night
with a secondary disturbance tracking south of it towards the
Southeast. As a third disturbance approaches from the Great Lakes,
a strengthening 250mb jet streak over the Northeast will work with
a second 250mb jet streak over the South to creating a classic
"coupling jet streak" setup off the Mid-Atlantic coast. This will
be the basis for a strengthening winter storm that tracks initially
through the Southeast Monday night and up the East Coast by Tuesday
afternoon.

The primary ingredients are generally agreed upon on all guidance,
although how they come together and where the storm tracks is=20
still coming into focus. High pressure over the Northeast will=20
initially provide a sufficiently cold air-mass to support wintry=20 precipitation at the onset from the Central Appalachians on north=20
and east, but it will be exiting off Atlantic Canada on Tuesday. As
925-700mb WAA advances north Monday night and into Tuesday, any=20
initial snow over the Central Appalachians will changeover to a=20 sleet/freezing rain mix, then all freezing rain. Cold air damming=20
(CAD) will linger long enough in the higher terrain to support=20
disruptive ice accumulations that result in slick travel conditions
Monday night and into Tuesday morning. WPC probabilities show >50%
chances for ice accumulations over a tenth of an inch from the=20
Blue Ridge of western NC on north through the mountains of western=20
VA and eastern WV. There are some low-chance probabilities (10-30%)
for over a quarter inch of ice from VA's Skyline Drive on south and west
to the WV/VA border. The latest WSSI does depict Minor to Moderate
Impacts in these regions with a focus on treacherous travel=20
conditions.

Farther north over the Mid-Atlantic, precipitation is likely to
start out as snow over northern VA/MD, southern PA, and on north
towards the NYC metro Tuesday morning. Guidance then begins to
disagree on the handling of the transition and northward expansion
of the snow-wintry mix area. Low-level SErly flow is strong enough
to where most areas along I-95 should flip over to plain rain on
Thursday morning, but farther inland over the Piedmont of VA,
northern MD, and Lower Susquehanna Valley, low-lvel cold may stick
around long enough for a wintry mix to hang around longer. This is
likely to be the region's first accumulating snowfall, so there are
likely to detrimental impacts to travel even if snowfall and ice
accumulations are minor (1-3" of snow for these areas, up to a=20
tenth of an inch of ice in western MD and northwest VA). However,=20
from the Lehigh Valley and Poconos on north and east through=20
northwest NJ, the Catskills, and into interior southern New=20
England, snow is likely to remain the primary precip type.

The storm by Tuesday afternoon will begin to develop a closed lower
over the Delaware Valley that deepens south of Long Island by
Tuesday evening. To the north and east of the 850mb low, a
consolidated 850-700mb FGEN area will develop and result in a band
of heavy snow somewhere from northeast PA and southern NY (north of
NYC) through southern New England. Snowfall rates within this band
are likely to at least top 1"/hr. There still remains some
uncertainty on where this band sets up, but probabilistic guidance
is showing increase odds on a snowfall swath of >6" from the
Poconos and Catskills on north and east. The higher terrain across
New England (Berkshires, Worcester Hills, Green, Whites, Downeast
Maine) are the most favored for locally heavy snowfall as WPC=20
probabilities shows low-to-moderate chances (30-50%) for over 12"=20
in some spots. The latest WSSI does depict Moderate Impacts due to
snow from western MA and northern CT to southern NH and southern=20
ME with locally Major Impacts possible.=20

In summary, this is going to be the first accumulating snow of the
season for many areas from southern PA to areas just west of I-95,
potentially including the Boston metro area should more southern
guidance come to fruition. Expect travel delays on Tuesday and into
Tuesday night in affected areas. High pressure and dry conditions
return to the Northeast by early Wednesday morning.=20

Key Messages remain in effect for this system and are linked below
(Key Message #3)


Mullinax



...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!4a3u3xvT3-hHMgEuVV19WxvIhLYs9AwNztPM6v7_Rvx-N= fA7rqvdw0CdltnXbH7K29K2qwndPvJ_PXi1VPNvhwlFOkk$=20



$$

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FOUS11 KWBC 010804
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
304 AM EST Mon Dec 1 2025

Valid 12Z Mon Dec 01 2025 - 12Z Thu Dec 04 2025


...Central Plains through the Mid-Atlantic & Northeast...=20
Days 1-3...

...Widespread moderate to heavy snow from the Central Plains to the
Northeast will impact travel early this week while treacherous
icing occurs across the Appalachians...

A potent but positively tilted mid-level shortwave trough will be
advancing eastward from the Four Corners to start the period /12Z
today/ and move progressively eastward into the Ohio Valley by
Tuesday morning. During this translation, the feature, while
remaining of modest amplitude, may take on at least a neutral tilt
as vorticity continues to swing through the base of the
accompanying parent trough, and the entire system should be off the
New England Coast by 12Z Wednesday with only subtle amplification
expected. Although this shortwave will remain modest overall, the
accompanying jet streaks, both a downstream intensifying feature
and the broader subtropical jet lifting out of Mexico, are expected
to phase across the southern/central Plains today. The increasing
ascent left by the resulting RRQ overlapping height falls from the
shortwave will result in surface cyclogenesis along the Gulf Coast
tonight. This surface low is then expected to track rapidly
northeast across the southern Mid-Atlantic states and then deepen
just inside the 40N/70W Benchmark Tuesday night before lifting into
into the Canadian Maritimes.

This evolution will result in widespread snow and freezing rain
across the eastern half of the country, with two distinct areas of
impactful wintry precipitation.

On the north side of this system, a swath of moderate snow is
expected on D1 from Kansas through the Ohio Valley. This is in
response to the strengthening/phased jet streak which will begin to
tilt poleward to support impressive upper diffluence. At the same
time, some mid-level frontogenesis will be intensified by this jet
streak, forcing favorable overlap of ascent into the deepening DGZ
(SREF probabilities for 100mb of depth over 30% now) which will
support heavy snowfall rates within a translating band of 1"/hr or
more at times, aided by fluffy SLRs. The guidance has trended=20
upward with this feature, and WPC probabilities indicate a 10-30%
chance for at least 4 inches of snow from near Kansas City through
just south of Chicago.


As this band moves east into the Ohio Valley, it will become=20
merged with the larger system developing near the Gulf as=20
impressive moist isentropic ascent begins and lifts a theta-e ridge
northward to expand the precipitation shield. The strong 850mb WAA
will provide additional ascent, with the accompanying fgen serving
to intensify omega into the DGZ. While the WAA will likely result=20
in a burst of moderate snowfall in many areas from the Mid-
Atlantic/Ohio Valley northeast, a lack of resupplying cold air as=20
the surface high retreats will enable a quick transition to=20
mixed/rain, especially along and east of I-95 between VA and MA.=20
However, NW of the I-95 corridor, a prolonged period of moderate to
at times heavy snow is likely, with 1+"/hr rates spreading from PA
to ME. This will create an axis of snowfall for which WPC=20
probabilities indicate a high risk (>70% chance) for 4+ inches from
the Poconos through Downeast Maine, with locally as much as 8-12=20
inches possible (50% chance) from the Berkshires through the=20
Monadnock region of NH and into southern ME.

It is important to add as well, that despite what should be a
relatively quick transition from snow to mix to rain along I-95,
the Tuesday morning commute could be significantly impacted.

South of the heavy snow axes, two areas of impactful freezing rain
are also anticipated. The first will be across portions of
AR/MO/KY, in the vicinity of the Ozarks on Monday morning as
isentropic ascent and the accompanying moisture plume spread
precipitation into this region. Initially, surface wet-bulb
temperatures will be sub-freezing, so precipitation will fall as
freezing rain in response to the warm nose pivoting overhead.
However, this p-type should generally be short lived except in the
coldest regions, and WPC probabilities for 0.1" of ice peak around
30% in central AR.

More significant icing is likely across portions of the central and
southern Appalachians as isentropic ascent and accompanying WAA
intensify Monday night into Tuesday. Here, wet-bulb temperatures
will again be below freezing leading to an extended period of
freezing rain from SW NC into western MD. Although the high
retreats, this cold air may be more challenging to scour out,
especially in the higher elevations, leading to an extended period
of freezing rain with impactful ice accretions likely. WPC
probabilities D1 into D2 suggest a high risk (>70%) for at least
0.1" of icing from western NC through the Shenandoah region of VA,
with a low chance (10-30%) of up to 0.25" in isolated locations.

Key Messages remain in effect for this system and are linked below
(Key Message #3)


...Northern to Southern Rockies...=20
Days 2-3...

A shortwave digging out of British Columbia embedded within broad
cyclonic flow across the eastern half of the CONUS will spread
increasing synoptic ascent across the Intermountain West beginning
Tuesday morning. This shortwave will move progressively southeast
Tuesday, and may become more amplified despite maintaining a strong
positive tilt by Wednesday morning in response to secondary
vorticity maxima digging through its base. This will result in a
slowing and amplification of the trough, with downstream ascent
maximizing through height falls, PVA, and downstream intensifying
jet energy.=20

Available moisture will generally be modest as reflected by near-
normal PW anomalies, but the overlapped synoptic lift will be more
than sufficient to wring this out as periods of moderate to heavy
snowfall across much of the terrain. At the same time, a wave of
low pressure is progged to drop southeast coincident with the
shortwave trough, and a secondary front will also push south out of
Canada to cool the column while additionally leading to localized
upslope flow. Despite a shallow DGZ noted in regional forecast
soundings, the best ascent may maximize within this snow growth
region to enhance snowfall, and this suggests a broad swath of
moderate snow is likely Tuesday and Wednesday across much of the
Rockies.

WPC probabilities for 4+ inches D2 are highest from MT through WY,
with local maxima in snowfall above 8 inches possible across the
Little Belts and Absarokas, with snow levels running around
2000-3000 ft. By D3, the heaviest snow pivots southeast reaching
the CO Rockies, the San Juans, and Sangre de Cristos, where WPC
probabilities indicate a moderate risk (50-70%) for 6+ inches of
snowfall. Snow levels continue to fall on Wednesday as well such
that even the I-25 urban corridor from Cheyenne to Santa Fe may
experience a few inches of snow, with the higher accumulations
expected across the Raton Mesa and Palmer Divide.


...Great Lakes & Northeast...
Day 3...

A strong arctic front will race across the Great Lakes Wednesday,
likely reaching Upstate NY by Thursday morning before continuing
into New England beyond this forecast period. While confidence is
low at this time, the signals appear favorable for snow squalls
along this front as it dives southeast. The trends in the GFS SnSq
parameter have decayed a bit in recent runs, but the environment at
this time frame appears at least marginally favorable for a line,
or lines, of convective snow showers/snow squalls Wednesday into
Thursday. While snowfall amounts will be minimal, snow squalls can
cause dangerous driving due to briefly heavy snow rates and gusty
winds, so this event will need to be monitored as it gets closer.


Weiss



...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!5yQB3jpQNoHGi7CLwb89D4XfQqfQD6y2WYs0GA0deyuOX= 5XM7r-Hwq9HUl0fa45gZku1edttTkTaRH-BsCW62nKKERs$=20



$$

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FOUS11 KWBC 012030
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
330 PM EST Mon Dec 1 2025

Valid 00Z Tue Dec 02 2025 - 00Z Fri Dec 05 2025


...Central Plains through the Mid-Atlantic & Northeast...=20
Days 1-2...

...Widespread moderate to heavy snow from the Central Plains to the
Northeast will impact travel early this week while treacherous
icing occurs across the Appalachians...

A positively-tilted upper trough will continue to move steadily
east of the Rockies, assuming a neutral tilt, with phasing streams
over the Plains early in the period. This trough will continue to=20
move east across the Midwest on Tuesday, reaching the East Coast=20
late in the day, before becoming negatively-tilted as it moves off=20
of the Mid Atlantic/Northeast coasts Tuesday night.=20

At the surface, low pressure will develop over the northern Gulf=20
tonight before energy transfers to low pressure along the=20
Southeast coast. Supported by a coupled upper jet, this low will=20
deepen quickly as it tracks north along the Mid Atlantic to the=20
Northeast coast on Tuesday. With the 12Z ECMWF now shifted north,=20
the general consensus of the deterministic runs and the ensemble=20
means show the low tracking near the 40N/70W benchmark around 00Z=20
Wednesday before continuing on a track east of the Canadian=20
Maritimes Wednesday morning.

Upper level forcing along with low-to-mid level frontogenesis will
continue to support light to moderate snow spreading east from the
mid Mississippi through the Ohio valleys tonight, with the latest=20
WPC probabilities indicating that accumulations for most areas will
remain under 4 inches.

As this band moves east into the Ohio Valley, it will merge with=20
the larger system developing near the Gulf as impressive moist=20
isentropic ascent supports a north-moving theta-e ridge and an=20
expanding precipitation shield. Strong 850mb WAA will provide=20
additional ascent, with the accompanying frontogenesis serving to=20
intensify omega into the DGZ. While the WAA will likely result in a
burst of moderate snowfall in many areas across the interior Mid=20
Atlantic into the Northeast, a lack of resupplying cold air as a=20
surface high to the north retreats will enable a quick transition=20
to mixed/rain, especially along and east of the I-95 corridor from
northern Virginia to Boston. The 12Z models trended slightly=20
warmer, further indicating that areas from DC to NYC will be=20
mostly, if not entirely, all rain. However, northwest of the I-95=20
corridor, the story remains much different, where a prolonged=20
period of moderate, to at times heavy snow, is likely, with 1+"/hr=20
rates spreading from Pennsylvania to Maine. This will create an=20
axis of snowfall for which WPC probabilities continue to show a=20
high risk (>70% chance) for 4+ inches from the Poconos through=20
Downeast Maine, with locally as much as 8-12 inches possible (50%=20
chance) across parts of the Catskills and from the Berkshires to=20
southern Maine, including the northern Worcester Hills and=20
Monadnock region.

South of the heavy snow axes, light ice accumulations will shift
northeast from southern Arkansas into eastern Tennessee and=20
Kentucky. WPC probabilities indicate that where ice does
accumulate it will remain under 0.10 inch for most areas.

Meanwhile, more significant icing is likely to develop starting=20
tonight across portions of the central and southern Appalachians as
isentropic ascent and accompanying WAA intensify. Subfreezing wet-
bulb temperatures will support an extended period of freezing rain
along the southern to central Appalachians from North Carolina to=20
western Maryland. Although the high to the north will be=20
retreating, this cold air may be more difficult to scour out,=20
especially in the more sheltered locations, leading to an extended=20
period of freezing rain with impactful ice accretions likely. WPC=20 probabilities show 50 percent or greater probabilities for at least
0.1 inch of ice from across parts of western North Carolina=20
northward along the southern Blue Ridge into southern West Virginia
and the Shenandoah region of Virginia, with a low chance (10-30%)=20
of up to 0.25 inch in isolated locations.

Key Messages remain in effect for this system and are linked below
(Key Message #3)


...Northern to Southern Rockies...=20
Days 1-3...

A shortwave will dig south out of British Columbia into the
northwestern U.S. overnight. This shortwave will continue to move=20
southeast Tuesday into Wednesday, and may become more amplified as
it drops through the Great Basin in response to secondary=20
vorticity maxima digging through its base. This will result in a=20
slowing and amplification of the trough, with downstream ascent=20
maximizing through height falls, PVA, and downstream intensifying=20
jet energy.=20

Available moisture will generally be modest as reflected by near-
normal PW anomalies, but the overlapped synoptic lift will be more
than sufficient to wring this out as periods of moderate to heavy
snowfall across much of the terrain. At the same time, a wave of
low pressure is progged to drop southeast coincident with the
shortwave trough, and a secondary front will also push south out of
Canada to cool the column while additionally leading to localized
upslope flow. Despite a shallow DGZ noted in regional forecast
soundings, the best ascent may maximize within this snow growth
region to enhance snowfall, and this suggests a broad swath of
moderate snow is likely Tuesday and Wednesday across much of the
Rockies.

WPC probabilities for 4+ inches Day 1 are highest from northwestern
Montana to northwestern Wyoming and northern Idaho, with local=20
maxima in snowfall above 8 inches possible across the higher
terrain. By Day 2, the heaviest snow pivots southeast reaching the
central Rockies, notably the Colorado ranges, where most of the
higher probabilities for accumulations above 4 inches are=20
centered. The southern shift is expected to continue into Day 3,=20
with the Sangre de Cristos in northern New Mexico the focus for the
higher probabilities for amounts over 4 inches.

...Great Lakes & Northeast...
Day 3...

A strong arctic front will race across the Great Lakes Wednesday,
likely reaching Upstate NY by Thursday morning before continuing
into New England. The signals appear favorable for snow squalls=20
along this front as it dives southeast. The trends in the GFS SnSq=20
parameter remain fairly muted, however the NAM ramps up notably
across parts of Pennsylvania and Upstate NY into New England on
Thursday. While snowfall accumulations will be minimal, snow=20
squalls can cause dangerous driving due to briefly heavy snow rates
and gusty winds, so this event will need to be monitored as it=20
gets closer.

Pereira/Weiss

...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!6oXhXucCqMO6rFQZw4LhD3-riI-5FAbKI4WO1sf2hP8LT= oEz6p5IVVzBv2VrbH0G1tj2lmGYpsUo2RcvZ2Kbm3cNMKo$=20


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FOUS11 KWBC 020730
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
230 AM EST Tue Dec 2 2025

Valid 12Z Tue Dec 02 2025 - 12Z Fri Dec 05 2025


...Mid-Atlantic & Northeast...=20
Days 1...

...Rapidly deepening coastal low will bring heavy snow to the
interior Mid-Atlantic and Northeast today/tonight...

Low pressure will move off the NC/VA coast this morning and then
track rapidly northeast along the coast, passing inside the 40N/70W
benchmark before lifting into the Canadian Maritimes by Wednesday
morning. The overlap of height falls, a coupled jet streak, and the
latent heat release along the offshore baroclinic gradient will
allow the low to rapidly deepen during this period, spreading
heavy precipitation and gusty winds into the Northeast.

As the low moves up the coast, persistent and impressive moist
isentropic ascent will surge a theta-e ridge northward to support
expanding heavy precipitation. The coincident WAA at 850mb will
produce additional ascent, with intensifying fgen driving some
banded precipitation, but also warm the column aloft as the surface
high pressure retreats rapidly to the east. The guidance has
trended just a bit warmer again overnight, and while most areas
along I-95 and points west will likely start as a brief period of
snow/sleet, any meaningful accumulation is anticipated only well
inland and at higher elevations, especially in southern and central
New England. The big cities from Washington, D.C. to Boston, MA may
start as snow before changing over to rain (and Boston may change
back to snow briefly before the system exits Wednesday morning).
However, well NW, WPC probabilities are high (>70%) for at least 6
inches of snow from the Catskills through the Berkshires, the
Worcester Hills, and across much of southern NH and ME (away from
the immediate coast) where locally as much as 12 inches is possible
(10-30% chance).

Additionally, while most of the freezing rain accompanying this
system is expected to wane before 12Z/Tuesday, an additional 0.1"
of ice is possible (10-30% chance) across the Central Appalachians
in the vicinity of Shenandoah NP.

Key Messages remain in effect for this system and are linked below
(Key Message #3)


...Northern to Southern Rockies...=20
Days 1-2...

A shortwave digging south out of British Columbia into the=20
northwestern U.S. will be positioned across the interior Northwest
to begin the forecast period /12z Tuesday/. This shortwave will=20
continue to move southeast through Wednesday, and may become more=20
amplified as it drops through the Great Basin in response to=20
secondary vorticity maxima digging through its base. This will=20
result in a slowing and amplification of the trough, with=20
downstream ascent maximizing through height falls, PVA, and=20
downstream intensifying jet energy, especially as it approaches the
Four Corners Wednesday morning.

Available moisture will generally be modest as reflected by near-
normal PW anomalies, but the overlapped synoptic lift will be more
than sufficient to wring this out as periods of moderate to heavy
snowfall across much of the terrain. At the same time, a wave of
low pressure is progged to drop southeast coincident with the
shortwave trough, and a secondary front will also push south out of
Canada to cool the column while additionally leading to localized
upslope flow. Despite a shallow DGZ noted in regional forecast
soundings, the best ascent is progged to intersect within this=20
snow growth region to enhance snowfall, and this suggests a broad=20
swath of moderate snow is likely today and Wednesday across much=20
of the Rockies.

WPC probabilities D1 for 6+ inches are highest in the terrain above
5000 ft from the Salmon River/Sawtooth Range of ID through the
Absarokas, Little Belts, Tetons, and down into the Park Range and
other CO Rockies. During D2, the highest probabilities shift south
with the shortwave and increase, reaching above 80% for 6+ inches
along much of the Sangre de Cristos where locally 12+ inches is
likely. Additionally, as this shortwave digs south, some moderate
snowfall is likely along the I-25 urban corridor of Colorado,
bringing some notable snow to a region that has yet to experience
much so far this winter.

...Great Lakes & Northeast...
Day 3...

A strong arctic front will race across the Great Lakes Wednesday,
likely reaching Upstate NY by Thursday morning before continuing
into New England and crossing offshore into the Atlantic Thursday
night. Environmental signals continue to appear favorable for snow
squalls along this front as it dives southeast, and the GFS and NAM
SnSQ parameter have both increased tonight, especially from western
PA through northern New England where a significant overlap of
0-2km fgen and SBCAPE as high as 200 J/kg exists in a region of
elevated low-level RH. This suggests increasing confidence in
linear snow squalls, especially Thursday. While snowfall=20
accumulations from this event will likely be minimal, brief intense
snow rates combined with gusty winds may create dangerous travel=20
across parts of the northern Great Lakes and interior Northeast.

Weiss


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!9CitJsY81sgfvgcKlG6ZrnnEIhWwB6pKIFXM58UDsWGWr= 9HKJE7T1O8YkkonalX1bNrkX6KvtEsUu9UtiQFpNXUEnak$=20



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FOUS11 KWBC 022034
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
334 PM EST Tue Dec 2 2025

Valid 00Z Wed Dec 03 2025 - 00Z Sat Dec 06 2025


...Northeast...=20
Days 1...

Low pressure now moving north along the Mid Atlantic coast will
deepen rapidly through the evening as the associated shortwave
trough moves through the Northeast/Mid Atlantic, and assumes a
negative tilt as it moves offshore. This system will move quickly
overnight, tracking from near the 40N/70W benchmark at 00Z to east
of Nova Scotia by daybreak. The back edge of the associated=20
precipitation shield will move quickly to the east as well, with=20
snowfall ending for most areas apart from coastal northern New=20
England by tomorrow morning. Additional snowfall accumulations=20
after 00Z are expected to be light for most areas, with WPC=20
probabilities indicating the chance for accumulations greater than=20
4 inches are negligible for most areas, with some 10-30=20
probabilities confined to coastal Maine and southern New Hampshire.

...Northern to Southern Rockies...=20
Days 1-2...

A low amplitude shortwave trough dropping through the Pacific
Northwest today is forecast to amplify as it digs south along the=20
Sierra Nevada/Great Basin overnight, with the model consensus=20
showing a well-defined positively-tilted trough dropping into the=20 Southwest/Four Corners on Wednesday. Meanwhile at the surface, a cold
front will settle south into the southwestern U.S. A low level=20
circulation developing and dropping south through western Colorado=20
will help to enhance snowfall over the western Colorado ranges,=20
notably the San Juans, where WPC guidance shows some isolated=20
higher probabilities for accumulations greater than 6 inches on Day
1. More widespread higher amounts are expected to develop along=20
the eastern ranges from the Front Range south to the northern=20
Sangre de Cristos - supported by increasing upslope flow on the=20
backside of a sharp ridge nosing south along the High Plains.

=46rom Wednesday night into early Thursday, the shortwave over the
Southwest will begin to eject east, focusing snow further south
over the Rockies. Amounts are expected to me mostly light, with WPC probabilities indicating amounts over 6 inches will remain mostly
confined to the higher peaks of the southern Sangre de Cristos.


...Great Lakes & Northeast...
Days 1-3...

An arctic front associated with an amplifying trough over eastern=20
Canada will sweep across the upper Great Lakes on Wednesday,
setting off a period of lake effect snow showers that will continue
into early Thursday before a shortwave ridge moves over the region.
Overall, accumulations for the two-day period are expected to be=20
generally light. Although some parts of the eastern U.P. are likely
to see totals over 4 inches.

Meanwhile, the previously noted front will advance east of the
lakes, moving across the Northeast on Thursday. While heavy
accumulations along the front are not expected, snow squalls remain
a concern, with the NAM continuing to show some notable Snow=20
Squall Parameter values as the front advances across Upstate New=20
York and New England. This indicates a brief period of intense=20
snowfall that is likely to reduce visibilities and impact travel.=20
Behind the front, lake effect snow showers will develop briefly off
of lakes Erie and Ontario Wednesday night into Thursday, with the=20
best chance for heavy accumulations centered over the Tug Hill=20
region.

The aforementioned shortwave ridging is forecast to develop ahead
of another shortwave that is expected to dive southeast across
central Canada on Thursday and amplify as it brushes the upper=20
Great Lakes Friday morning. Most of the better forcing and lake
enhancement is expected to remain north of the lakes; however some
lighter amounts are likely, especially over northern Michigan.=20


...Mid South to the Mid Atlantic...
Day 3...

The previously noted shortwave over the Southwest will move east of
the southern Rockies on Thursday, becoming less amplified as it
moves into a region of confluent upper flow. However it will
provide enough lift to spread some light precipitation north into
the Mid South/Tennessee Valley, with a low end chance for some=20
light wintry precipitation/ice accumulations Thursday night into=20
early Friday. A greater chance for light snow/ice accumulations is=20
expected to develop farther east over the southern Appalachians,=20
where a cold air wedge is forecast to linger long enough to support
at least some minor accumulations on Friday.=20

Pereira

...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!5dX0zkdWbchHEQyfBkNAry9V7K3ebVmkRcD5w6GTZEdic= Rf4ygZ7kFSH-wJMsfxpoP2Zrn2TyshbLy4IoKDLGbL13OA$=20



$$

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FOUS11 KWBC 022051
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
351 PM EST Tue Dec 2 2025

Valid 00Z Wed Dec 03 2025 - 00Z Sat Dec 06 2025


...Northeast...=20
Days 1...

Low pressure now moving north along the Mid Atlantic coast will
deepen rapidly through the evening as the associated shortwave
trough moves through the Northeast/Mid Atlantic, and assumes a
negative tilt as it moves offshore. This system will move quickly
overnight, tracking from near the 40N/70W benchmark at 00Z to east
of Nova Scotia by daybreak. The back edge of the associated=20
precipitation shield will move quickly to the east as well, with=20
snowfall ending for most areas apart from coastal northern New=20
England by tomorrow morning. Additional snowfall accumulations=20
after 00Z are expected to be light for most areas, with WPC=20
probabilities indicating the chance for accumulations greater than=20
4 inches are negligible for most areas, with some 10-30=20
probabilities confined to coastal Maine and southern New Hampshire.

...Northern to Southern Rockies...=20
Days 1-2...

A low amplitude shortwave trough dropping through the Pacific
Northwest today is forecast to amplify as it digs south along the=20
Sierra Nevada/Great Basin overnight, with the model consensus=20
showing a well-defined positively-tilted trough dropping into the=20 Southwest/Four Corners on Wednesday. Meanwhile at the surface, a cold
front will settle south into the southwestern U.S. A low level=20
circulation developing and dropping south through western Colorado=20
will help to enhance snowfall over the western Colorado ranges,=20
notably the San Juans, where WPC guidance shows some isolated=20
higher probabilities for accumulations greater than 6 inches on Day
1. More widespread higher amounts are expected to develop along=20
the eastern ranges from the Front Range south to the northern=20
Sangre de Cristos - supported by increasing upslope flow on the=20
backside of a sharp ridge nosing south along the High Plains.

=46rom Wednesday night into early Thursday, the shortwave over the
Southwest will begin to eject east, focusing snow further south
over the Rockies. Amounts are expected to me mostly light, with WPC probabilities indicating amounts over 6 inches will remain mostly
confined to the higher peaks of the southern Sangre de Cristos.


...Great Lakes & Northeast...
Days 1-3...

An arctic front associated with an amplifying trough over eastern=20
Canada will sweep across the upper Great Lakes on Wednesday,
setting off a period of lake effect snow showers that will continue
into early Thursday before a shortwave ridge moves over the region.
Overall, accumulations for the two-day period are expected to be=20
generally light. Although some parts of the eastern U.P. are likely
to see totals over 4 inches.

Meanwhile, the previously noted front will advance east of the
lakes, moving across the Northeast on Thursday. While heavy
accumulations along the front are not expected, snow squalls remain
a concern, with the NAM continuing to show some notable Snow=20
Squall Parameter values as the front advances across Upstate New=20
York and New England. This indicates a brief period of intense=20
snowfall that is likely to reduce visibilities and impact travel.=20
Behind the front, lake effect snow showers will develop briefly off
of lakes Erie and Ontario Wednesday night into Thursday, with the=20
best chance for heavy accumulations centered over the Tug Hill=20
region.

The aforementioned shortwave ridging is forecast to develop ahead
of another shortwave that is expected to dive southeast across
central Canada on Thursday and amplify as it brushes the upper=20
Great Lakes Friday morning. Most of the better forcing and lake
enhancement is expected to remain north of the lakes; however some
lighter amounts are likely, especially over northern Michigan.=20


...Mid South to the Mid Atlantic...
Day 3...

The previously noted shortwave over the Southwest will move east of
the southern Rockies on Thursday, becoming less amplified as it
moves into a region of confluent upper flow. However it will
provide enough lift to spread some light precipitation north into
the Mid South/Tennessee Valley, with a low end chance for some=20
light wintry precipitation/ice accumulations Thursday night into=20
early Friday. A greater chance for light snow/ice accumulations is=20
expected to develop farther east over the southern Appalachians,=20
where a cold air wedge is forecast to linger long enough to support
at least some minor accumulations on Friday.=20

...Northern Rockies...
Day 3...

The next chance for heavy snowfall totals in the northern Rockies
will develop as a low amplitude shortwave slides off of the top of
the Pacific ridge into the region late Thursday into Friday.=20
Favorable mid to upper level forcing along with a notable influx of
Pacific moisture will be sufficient for some heavy totals over the
northern Rockies from northern Idaho and western Montana to=20
western Wyoming -- where WPC probabilities indicate widespread=20
totals over 4 inches are likely, with amounts over 8 inches=20
possible in the higher terrain.=20

Pereira

...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_3.png__;!!DZ3fjg!_o-SUQXPmGVKCQUA40WQkjG6mxm--y--ExzoWHd0zGwiZ= t3WKbKCcaAGBk-7uBOjIe-o6HDQyb7eerxWCf07fenphZ0$=20



$$

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FOUS11 KWBC 030755
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
255 AM EST Wed Dec 3 2025

Valid 12Z Wed Dec 03 2025 - 12Z Sat Dec 06 2025


...Southern/Central Rockies...
Days 1-2...

Shortwave which emerged from British Columbia Monday will continue
to track southeast across the Four Corners today while amplifying.
The guidance has trended a bit farther south and more amplified
with the evolution today, which should result in heavier snowfall
especially across the San Juans and Sangre de Cristos on D1.
Forcing for ascent downstream of this trough (in response to height
falls and modest divergence) will be enhanced by a strengthening
jet streak, especially tonight into Thursday morning, and periods
of impressive upslope flow as cold N/NE winds develop in advance of
an Canadian high pressure dropping into the Plains. Moisture within
the region is progged to be around to slightly below normal as
reflected by NAEFS ensembles, but the impressive overlapping ascent
will still maximize favorable to support heavy snow, especially
above 4000-5000 ft, with snow levels falling in conjunction with
waning snowfall intensity. WPC probabilities, especially across the
San Juans and Sangre de Cristos, have increased tonight, and now
feature a high risk (>70%) for more than 12 inches in the higher
terrain of these ranges. Into the lower terrain, WPC probabilities
indicate a moderate threat (30-50%) for at least 4" along the I-25
urban corridor, with locally more than 6" in the higher terrain of
the Raton Mesa and southern Palmer Divide.


...Great Lakes & Northeast...
Days 1-3...

Progressive flow across the Northeast will manifest in response to
a large gyre centered near Hudson Bay, which will shed periodic
shortwaves from the Great Lakes through the Northeast leading to
occasional enhanced ascent and lowered heights throughout. In
response to this evolution, the period will remain active through
LES and arctic fronts, and multiple rounds of snowfall, sometimes
heavy, are expected.

The first event will be associated with an arctic cold front
dragging southeast beneath a shortwave aloft. This front will
likely move rapidly across the Great Lakes today, and then across
the Northeast Thursday. Along and ahead of this front, the
environment continues to suggest an increasing threat for snow
squalls, especially across PA/NY and New England on Thursday. The
NAM SnSq parameter continues to be more aggressive than the GFS,
but the antecedent low-level environment ahead of the front appears
favorable for squall development. With 0-2km fgen maximizing along
the front into elevated RH and SBCAPE as high as 300 J/kg,
widespread linear squalls could result. Upstream into MI the threat
is not as high on D1, and although isolated squalls could occur,
the greater risk will be D2 in the Northeast. While total snowfall
will be minimal in any squall, rapidly changing conditions due to
heavy snow and gusty winds will create periods of dangerous travel
Thursday aftn. These squalls could become widespread, and after
coordination with the northeast WFOs, it is possible that with
future model cycles some enhanced messaging may be needed to
highlight the threat.

Behind this front, as well as behind a subsequent shortwave on
Friday, increased CAA will spread across the Great Lakes leading to
periods of lake effect snow (LES). The progressive flow will
support shortwave ridging between the two impulses, so the duration
of any LES with each shortwave/front should be somewhat limited.
However, 850mb temps falling to -15C to -20C Wednesday
night/Thursday, and then -10C to -15C late Friday, will create
steep lapse rates and deepening inversion depths to support bands
of heavy LES. The heaviest LES snowfall accumulations within the
LES bands are expected in the typical NW snow belts across the U.P.
of MI, the NW L.P. near Traverse City, and then along the
Chautauqua Ridge and into the Tug Hill Plateau. In these belts,
3-day snowfall of 6-12 inches is possible, highest across the U.P.


...Mid-South to the Mid-Atlantic...
Day 3...

Uncertainty abounds D3 with respect to a strung-out shortwave
exiting the Central Plains and becoming embedded within the more
zonal flow to the east. Although this shortwave is expected to be
of modest amplitude and fast moving, the accompanying upper jet is
progged to be powerful at over 150kts across the Mid-Atlantic,
leading to surface low pressure development across the Southeast.
This low will then race E/NE, producing a swath of at least light
wintry precipitation from the Tennessee Valley to the Mid-Atlantic
states.

There has been at least a modest northward shift/trend in the MSLP
fields from the various global ensembles the past few runs, and
while the ECMWF operational remains the most aggressive/north, that
solution cannot be ruled out. In fact, the trends in the 250mb jet
streak and from evaluation of the clusters (for which the primary
variance is the amplitude of the trough across the east) could
suggest a more subtle northward track of this low which would shift
more wintry precipitation into the area. It is still too early to
iron out these details, but at least a low-end risk for a few
inches of snow is possible as reflected by WPC probabilities which
reach 10-30% for 1+ inches of snow across the Central Appalachians
and into eastern VA/MD. This is notably lower than the recent NBM probabilities, and the trends continue to increase, so it is worth
watching the evolution of this event during the next few days.

South of the potential moderate snow, an axis of light freezing
rain is also possible where a p-type transition occurs. While the
location of the heaviest icing is also uncertain, current WPC
probabilities indicate a 10-30% chance for at least 0.1" of ice
across northern NC and into southern VA.


...Northern to Central Rockies...
Days 2-3...

The next chance for heavy snowfall totals in the northern Rockies
will develop as a low amplitude shortwave slides off of the top of
the Pacific ridge into the region late Thursday into Friday,
coincident with the LFQ of an impressive upper jet streak swinging
across the Northern Pacific. This will result in favorable mid to
upper level forcing along with a notable influx of Pacific
moisture, sufficient for some heavy totals , especially above
around 5000 ft as snow levels rise coincident with this moisture
plume moving into the area. Heavy snowfall accumulations are likely
D2 from the WA Cascades through the terrain of NW WY near
Yellowstone NP as reflected by WPC probabilities that suggest a
high risk (>70%) for 4+ inches, with impacts to many of the area
passes becoming likely.

Probabilities become even more impressive D3 across the higher
terrain from Glacier NP through Yellowstone NP including portions
of the Sawtooth/Salmon River ranges, Absarokas, terrain of NW WY,
and into the Park Range of CO. Here, WPC probabilities D3 reach
above 70% for 8+ inches, and D3 snowfall could be impressive above
generally 6000 ft where locally 1-2 feet is possible.

Weiss



$$

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FOUS11 KWBC 032015
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
315 PM EST Wed Dec 3 2025

Valid 00Z Thu Dec 04 2025 - 00Z Sun Dec 07 2025


...Southern/Central Rockies...=20
Day 1...

The sharp, positively-titled trough currently over the Four=20
Corners states will continue to translate eastward tonight before=20
ejecting into the central/southern Plains on Thursday. Forcing for=20
ascent downstream of this trough (in response to height falls and=20
modest divergence) will be enhanced by a strengthening jet streak,=20 especially tonight into Thursday morning. Meanwhile, Canadian high=20
pressure dropping into the Plains will result in impressive upslope
flow as cold N/NE winds develop in response. Moisture within the=20
region is progged to be around to slightly below normal as=20
reflected by NAEFS ensembles, but the impressive overlapping ascent
will still be favorable to support heavy snow. This will=20
especially be the case above 4000-5000 ft, with snow levels falling
in conjunction with waning snowfall intensity later tonight into=20
Thursday morning. The latest WPC probabilities continue to show=20
moderate to high chances (40-80%) for additional accumulations of=20

6 inches across portions of the southern San Juans and Sangre de=20

Cristo mountain ranges, with low to moderate chances (20-50%) of >8
inches.


...Great Lakes & Northeast...
Days 1-3...

Progressive flow across the Northeast will manifest in response to
a large gyre centered near Hudson Bay, which will shed periodic=20
shortwaves from the Great Lakes through the Northeast leading to=20
occasional enhanced ascent and lowered heights throughout. In=20
response to this evolution, multiple rounds of snowfall, sometimes=20
heavy, are expected through the period.=20

The first event will be associated with an arctic cold front=20
dragging southeast beneath a shortwave aloft. This front will move=20
rapidly across the eastern Great Lakes tonight, and then across the
Northeast on Thursday. Along and ahead of this front, the=20
environment continues to suggest an increasing threat for snow=20
squalls, especially across Upstate NY and New England on Thursday.=20
With 0-2km fgen maximizing along the front into elevated RH and=20
SBCAPE as high as 300 J/kg, widespread linear squalls are likely.=20
While total snowfall will be minimal in any squall, rapidly=20
changing conditions due to heavy snow and gusty winds will create=20
periods of dangerous travel Thursday afternoon and evening. As a=20
result, WPC has initiated Key Messages to highlight this event. See
the link below for more details.

Behind this front, as well as behind a subsequent shortwave on=20
Friday, increased CAA will spread across the Great Lakes leading to
periods of lake effect snow (LES). The progressive flow will=20
support shortwave ridging between the two impulses, so the duration
of any LES with each shortwave/front should be somewhat limited.=20
However, 850mb temps falling to between -15C to -20C Thursday, and=20
then between -10C to -15C late Friday into Saturday, will create=20
steep lapse rates and deepening inversion depths to support bands=20
of heavy LES. The heaviest LES snowfall accumulations within the=20
LES bands are expected in the typical NW snow belts across the U.P.
of MI, the NW L.P. near Traverse City, and then along the=20
Chautauqua Ridge and into the Tug Hill Plateau. In these belts,=20
3-day snowfall of 6-12 inches is possible, highest across the U.P.


...Mid-South to the Mid-Atlantic...=20
Day 2...

Plenty of uncertainty heading into Day 2 with respect to a strung-
out shortwave exiting the Central Plains and becoming embedded=20
within the more zonal flow to the east. Although this shortwave is=20
expected to be of modest amplitude and fast moving, the=20
accompanying upper jet is progged to be powerful at over 150kts=20
across the Mid-Atlantic, leading to surface low pressure=20
development across the Southeast. This low will then race E/NE,=20
producing a swath of at least light wintry precipitation from the=20
Tennessee Valley to the Mid-Atlantic states.=20

There has been at least a modest northward shift/trend in the=20
MSLP/QPF fields from the various global ensembles the past few=20
runs, with the ECMWF and various machine learning suites the=20
farthest north. While it still remains too early to iron out the=20
details, WPC probabilities of 1+ inches of snow across the Central=20 Appalachians and into eastern VA/MD have increased to 20-60%, with=20
the highest chances in the higher terrain of WV/VA. WPC=20
probabilities for 2+ inches are between 10-20% from eastern WV to=20
central VA.

South of the potential moderate snow, an axis of light
freezing rain is also possible where a p-type transition occurs
underneath a stubborn layer of low-level cold air. The latest WPC=20 probabilities maintain a 10-30% chance for at least 0.1" of ice=20
across northern NC and into southern VA.


...Northern to Central Rockies...=20
Days 1-3...

The next chance for heavy snowfall totals in the northern Rockies=20
will develop as a low amplitude shortwave slides off of the top of=20
the Pacific ridge into the region late Thursday into Friday,=20
coincident with the LFQ of an impressive upper jet streak swinging=20
across the Northern Pacific. This will result in favorable mid to=20
upper level forcing along with a notable influx of Pacific=20
moisture, sufficient for some heavy totals, especially above around
5000 ft as snow levels rise coincident with this moisture plume=20
moving into the area. Heavy snowfall accumulations are likely from=20
the WA Cascades through the terrain of NW WY near Yellowstone NP as
reflected by WPC probabilities that suggest a high risk (>70%) for
4+ inches, with impacts to many of the area passes becoming=20
likely.

Probabilities become even more impressive Day 2 and 3 across the=20
higher terrain from Glacier NP through Yellowstone NP including=20
portions of the Sawtooth/Salmon River ranges, Absarokas, terrain of
NW WY, northern Utah, and into the Park Range of CO. Here, WPC=20
probabilities Day 2 and 3 reach above 70% for 8+ inches, and Day 2=20
and Day 3 snowfall could be impressive above generally 6000 ft=20
where locally 1-2 feet is possible.

Miller/Weiss




...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!4ONBRMdITod6KQZeFxmplUpEcL6FhhdNmsyM3cstn2js_= 1Nv2iBrrRRCa5z0OsCbPZ1yd7WcRTVv4VpGUAMNxmUzroo$=20



$$

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FOUS11 KWBC 040755
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
255 AM EST Thu Dec 4 2025

Valid 12Z Thu Dec 04 2025 - 12Z Sun Dec 07 2025


...Great Lakes & Northeast...
Days 1-3...

A progressive and flow pattern over the Great Lakes will result in
periodic episodes of snow squalls and LES bands as a -AO/NAO regime
cuts off a large upper low over southeast Canada and builds a ridge
over Greenland and the Davis Strait. Today, an Arctic front=20
traversing the Great Lakes will act as a trigger at low-levels at
the same as the divergent left-exit region of a 250mb jet streak
places itself over the Northeast. Latest NAM shows 0-2km FGEN along
the front that is paired with a well-saturated low-level profile
and SBCAPE as high as 300 J/kg. As the front traverses the region,
the DGZ will grow within the 900-800mb layer and squalls will be
capable of producing bursts of heavy snow and gusty winds. While
snow accumulations will likely be limited in most cases due to the
squalls' progressive movement, surface and road temperatures=20
around freezing will drop into the 20s in wake of the front,=20
allowing for untreated surfaces to become icy and hazardous.=20
Whether it be by snow accumulating on all surfaces, melting and=20
refreezing on untreated surfaces, or the rapid reductions in=20
visibility, snow squalls have the potential to produce dangerous=20
driving conditions in the matter of seconds. WPC continues to issue
Key Messages for the snow squall threat for today (see Key=20
Messages link below).

In wake of the Arctic frontal passage, a pair of sheared shortwave
troughs within a broad cyclonic flow pattern will direct a pair of
frontal systems across the Great Lakes. Rounds of light-to-moderate
snowfall will ensue over the Upper Great Lakes Thursday night and
into Friday, with another cold kicking up additional LES bands in
the typical LES belts of the region. WPC probabilities show low-
to-moderate chances (30-50%) for snowfall totals >4" through Friday
and Saturday in Michigan's U.P., the western LES band belts of
Michigan's Mitten, and downwind of Lakes Erie and Ontario.


...Mid-South to the Mid-Atlantic...=20
Days 1-2...

Guidance is coming into better agreement on a winter setup that
is likely to produce some of the first winter hazards of the season
from the Mid-South to the Mid-Atlantic beginning today and lasting
through Friday. A shortwave trough over the south-central Plains=20
today will weaken as it makes its way east. Despite this 500mb=20
trough losing its punch, a strong ridge of high pressure over the=20
Bahamas and a large upper-low over Hudson Bay has led to the=20
formation of a robust 250mb jet streak oriented SW-NE over the=20
east-central U.S.. Beneath the diffluent right-entrance region, a=20
weak wave of low-pressure along central Gulf Coast will escort a=20
plume of Gulf moisture northeastward into a frigid air-mass of=20
early December. Overrunning moisture along a narrow 925-850mb front
from central AR on east to the southern Appalachians is set to=20
give rise to a potentially disruptive wintry mix. Ice accumulations
from the Little Rock-Memphis-Nashville metro areas will be light,=20
but given it is the first icing setup of the season, untreated=20
roads may become slick and treacherous for travelers, especially=20
for the Thursday PM rush hour and overnight Thursday.=20

As the upper trough approaches the Mid-Atlantic Thursday night,=20
enhanced 290K isentropic ascent and increasing 850-700mb WAA aloft=20
will foster periods of snow to develop from the central=20
Appalachians and Blue Ridge of WV/VA on east across the=20
central/southern VA Piedmont Thursday night and into Friday=20
morning. Similar to the Mid-South, this will be the first=20
accumulating snow of the season, likely resulting in hazardous=20
travel conditions on untreated surfaces. Farther south, an icy=20
over-running setup looks to unfold from the southern Appalachians=20
on east across northern NC. A wintry mix is likely to cause some=20
minor ice accumulations on roads, sidewalks, and vegetation Friday=20
morning and could cause travel delays.

WPC probabilities show moderate chances (40-60%) for snowfall=20
totals >2" from the Central Appalachians to south-central VA, which
does include portions of the Richmond, VA metro area. Localized
amounts topping 4" are possible in the Blue Ridge Mountains of
southwest VA. In terms of ice accumulations, most areas from the
Mid-South to the Mid-Atlantic can expect ice accumulations less
than a tenth of an inch, although some of the southern Appalachians
of NC could see localized amounts approach one-tenth. The WSSI does
depict localized areas of Minor Impacts through Friday.


...Pacific Northwest, Northern & Central Rockies...
Days 1-3...

A highly active storm track into the Northwest will usher in
copious amounts of Pacific moisture from the Pacific Northwest on
east into the Northern and Central Rockies. Starting today, a
steady barrage of >90th climatological percentile PWATs will stream
across the Pacific Northwest and will over into the Great Basin=20
and Rockies through Friday and linger into Saturday. Synoptic-scale
forcing will be present throughout the Northern Rockies through=20
Friday, then over the Central Rockies late Friday into Saturday as
a stubborn NW-SE oriented 250mb jet streak places its diffluent=20
left-exit region overhead. Snow levels over the Pacific Northwest=20
will dip as low as 3,000ft while the Northern Rockies generally=20
hover around 4,000ft. As height falls ensue on Friday and continue
into Saturday, snow levels will drop to as low as 2,000ft,=20
although the heaviest snowfall will be confined to elevations above
5,000ft in the Bitterroots, Lewis Range, and Sawtooth, above=20
6,000ft in the Tetons, Absaroka, Big Horns, Bear River, and Wasatch
Ranges, and above 7,000ft in the central WY/CO Rockies.=20

Probabilities become even more impressive Day 2 and 3 across the=20
higher terrain from Glacier NP through Yellowstone NP including=20
portions of the Sawtooth/Salmon River ranges, Absarokas, terrain of
NW WY, northern Utah, and into the Park Range of CO. Here, WPC=20
probabilities Day 2 and 3 reach above 70% for 8+ inches, and Day 2=20
and Day 3 snowfall could be impressive above generally 6000 ft=20
where locally 1-2 feet is possible. Over the next few days, WPC
probabilities paint a wintry picture across many of the Northern
and Central Rockies, as well as the higher elevations of the=20
Cascades (above 5,000ft) with high chances (>70%) for snowfall
totals >12" in all of these listed ranges and elevations through
Saturday. In fact, the higher elevations of the Lewis Range,
Bitterroots, and Tetons have moderate-to-high chances (50-80%) for
snowfall totals >24". The WSSI shows many areas of Minor Impacts=20
of the Northern and Central Rockies, including some Moderate to=20
locally Major Impacts. The Major Impact potential areas=20
(considerable disruptions; dangerous travel and widespread=20
closures) along the Wasatch east of Salt Lake City. Residents in=20
these mountain ranges should prepare for a multi-day stretch of=20
winter weather that results in difficult and treacherous travel=20
conditions.

...Midwest...
Day 3...

The active pattern of Pacific moisture and disturbances traversing
the Northwest will result in at least one of these disturbances
reaching the Midwest late Friday night and into Saturday. A general
model consensus agrees a slug of rich Pacific moisture within the
700-300mb layer will advance across the northern Great Plains and
reach the Missouri River Valley by Saturday. This is where the
agreement in guidance ends, however, as individual guidance members
(including ensembles) disagree upon the strength and track of this=20
storm as it reaches the Central Plains on Saturday. The synoptic-=20
scale setup should foster an 850mb low with sufficient 850-700mb=20
FGEN to give rise to a band of moderate-to-heavy snow, but exactly=20
where this band sets up is low confidence.=20

At the moment, WPC probabilities show minor snowfall totals (1-3")
generally having moderate-to-high chances (30-50%) across the=20
northern High Plains through Saturday morning. The high degree of=20
spread in model solutions is causing WPC probabilities to sport low
chances (10-30%) for snowfall totals >4" from southeast SD and=20
northeast NE on east through southern MN and northern IA. That=20
being said, the favorable synoptic and mesoscale processes at play=20
could very much support a band of >6" snowfall totals that causes=20
travel headaches for residents in the Midwest. Those in the Midwest
should continue to monitor the forecast closely as more snow is in
the forecast and is likely to cause some travel headaches (WSSI-P=20
shows 40-60% chances for Minor Impacts from southeast SD and=20
northeast NE on east through southern MN and northern IA) but=20
details as to which areas are likely to see the worst impacts are=20
still unclear at this time.

Mullinax


...Winter Storm Key Messages are in effect. Please see current=20
Key Messages below...

https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/key_messages/Late= stKeyMessage_1.png__;!!DZ3fjg!-wJ58ymkpysFxygKi1ghMuAJzz62G2BeQhLjLlRE1QtRe= gwW2cnJ4DMLjWxp4ol_eRJ292Trto_NlWn0sb-kn78UBsc$=20



$$

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FOUS11 KWBC 042010
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
310 PM EST Thu Dec 4 2025

Valid 00Z Fri Dec 05 2025 - 00Z Mon Dec 08 2025


...Great Lakes...
Days 1-3...

Periodic mid/upper level impulses rotating within a broad cyclonic
flow pattern will continue to support rounds of light-to-moderate
lake effect snowfall across the upper Great Lakes the next few
days. WPC probabilities continue to show low-to-moderate chances
(30-60%) for snowfall totals >4" each day Friday through Sunday,
primarily across eastern portions of the U.P. of Michigan as well
as northern parts of Michigan's Mitten. Slightly higher
probabilities for lower snowfall amounts exist downwind of Lake
Erie and Lake Ontario on Sunday.


...Mid-South to the Mid-Atlantic...
Day 1...

The first winter hazards of the season from the Mid-South to the
Mid-Atlantic continue tonight into Friday as a developing wave of
low pressure along the central Gulf Coast escorts a plume of Gulf
moisture northeastward into a frigid air-mass for early December.
Overrunning moisture along a narrow 925-850mb front from central AR
on east to the southern Appalachians is set to give rise to a
potentially disruptive wintry mix. Ice accumulations from the
Little Rock-Memphis-Nashville metro areas will be light, but given
it is the first icing setup of the season, untreated roads may
become slick and treacherous for travelers through the overnight
hours tonight.

As weak low pressure slides eastward along the Gulf Coast,
enhanced 290K isentropic ascent, increasing 850-700mb WAA aloft,
and strengthening frontogenesis will foster periods of snow to
develop from the central Appalachians and Blue Ridge of WV/VA on
east across the central/southern VA Piedmont tonight and into
Friday morning. Latest trends also suggest the northern extent of
the snow shield likely reaching into the Baltimore/Washington
Metros late tonight into early Friday morning. Similar to the Mid-
South, this will be the first accumulating snow of the season,
likely resulting in hazardous travel conditions on untreated
surfaces. Farther south, an icy overrunning setup looks to unfold
from the southern Appalachians on east across northern NC. A wintry
mix is likely to cause some minor ice accumulations on roads,
sidewalks, and vegetation Friday morning and could cause travel
delays.

WPC probabilities have increased with this forecast package, now
showing moderate to high chances (50-90%) for snowfall totals >2"
from the Central Appalachians to south-central VA, which does
include portions of the Richmond, VA metro area. Localized amounts
topping 4" are possible in the Blue Ridge Mountains of southwest VA
and southern WV. In terms of ice accumulations, most areas from
the Mid-South to the Mid-Atlantic can expect ice accumulations less
than a tenth of an inch, although some of the southern
Appalachians of NC could see localized amounts approach one-tenth.
The WSSI does depict localized areas of Minor Impacts through
Friday.


...Pacific Northwest, Northern & Central Rockies...
Days 1-3...

A highly active storm track into the Northwest will usher in
copious amounts of Pacific moisture from the Pacific Northwest on
east into the Northern and Central Rockies. A steady barrage of

90th climatological percentile PWATs will stream across the

Pacific Northwest into the Great Basin and Rockies Friday into
Sunday. Synoptic-scale forcing will be present throughout the
Northern Rockies through Friday, then over the Central Rockies late
Friday into Saturday as a persistent NW-SE oriented 250mb jet
streak places its diffluent left exit region overhead. Snow levels
over the Pacific Northwest will dip as low as 3,000ft while the
Northern Rockies generally hover around 4,000ft. As height falls
ensue on Friday and continue Saturday into Sunday, snow levels will
drop to as low as 2,000ft, although the heaviest snowfall will be
confined to elevations above 5,000ft in the Bitterroots, Lewis
Range, and Sawtooth, above 6,000ft in the Tetons, Absaroka, Big
Horns, Bear River, and Wasatch Ranges, and above 7,000ft in the
central WY/CO Rockies.

Probabilities are impressive Day 1 and 2 across the higher terrain
from Glacier NP through Yellowstone NP including portions of the Sawtooth/Salmon River ranges, Absarokas, terrain of NW WY, northern
Utah, and into the Park Range of CO. Here, WPC probabilities Day 1
and 2 reach above 70% for 8+ inches, and Day 1 and Day 2 snowfall
could be impressive above generally 6000 ft where locally 1-2 feet
is possible. Over the next few days, WPC probabilities paint a
wintry picture across many of the Northern and Central Rockies, as
well as the higher elevations of the Cascades (above 5,000ft) with
high chances (>70%) for snowfall totals >12" in all of these listed
ranges and elevations through Saturday. In fact, the higher
elevations of the Lewis Range, Bitterroots, and Tetons have
moderate-to-high chances (50-80%) for snowfall totals >24".
Moderate to heavy snow continues into Day 3, though probabilities
are less compared to Days 1 and 2. The WSSI shows many areas of
Minor Impacts of the Northern and Central Rockies, including some
Moderate to locally Major Impacts. The Major Impact potential areas (considerable disruptions; dangerous travel and widespread
closures) along the Wasatch east of Salt Lake City. Residents in
these mountain ranges should prepare for a multi-day stretch of
winter weather that results in difficult and treacherous travel
conditions.


...Midwest...
Days 2-3...

The active pattern of Pacific moisture and disturbances traversing
the Northwest will result in at least one of these disturbances
reaching the Midwest late Friday night into Saturday. A general
model consensus agrees a slug of rich Pacific moisture within the
700-300mb layer will advance across the northern Great Plains and
reach the Missouri River Valley by Saturday. While the latest
models still disagree somewhat on the strength and track of this
storm as it reaches the Central Plains on Saturday and then the
Upper Midwest Saturday night into Sunday, the synoptic-scale setup
should foster an 850mb low with sufficient 850-700mb FGEN to give
rise to a band of moderate-to-heavy snow. Right now, this appears
to be most likely from southeast South Dakota and northeast
Nebraska to southwest Minnesota and northwest Iowa.

The latest WPC probabilities have increased with this forecast,
now supporting 48-hour (Days 2-3) probabilities of 30-70% for
snowfall totals >4" for locations that banding (mentioned above) is
most likely. Additionally, 48-hour probabilities of >8", while low
(10-15%) are non-zero across southwest Minnesota and northwest
Iowa, suggesting that the favorable synoptic and mesoscale
processes at play could very much support a band of >6" snowfall
totals that cause travel headaches for residents in the Midwest.
Those in the Midwest should continue to monitor the forecast
closely as additional increases in probabilities are possible with
future forecast packages.


Miller/Mullinax





$$

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FOUS11 KWBC 050815
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
315 AM EST Fri Dec 5 2025

Valid 12Z Fri Dec 05 2025 - 12Z Mon Dec 08 2025


...Great Lakes...
Days 1-2...

Periodic mid/upper level impulses rotating within a broad cyclonic
flow pattern will continue to support rounds of light-to-moderate
lake effect snowfall across the upper Great Lakes through Saturday.
Friday features modest WAA over the Great Lakes via SWrly flow that
looks to produce periods of snow over the northwestern towns of
Michigan's Mitten, while a cold frontal passage on Saturday
revitalizes LES bands over the Michigan U.P. and downwind of Lake
Ontario over the Tug Hill. WPC probabilities show low-to-moderate
chances (30-60%) for snowfall totals >4" over northwest mainland
Michigan today. By Saturday, most snowfall totals over the eastern
Michigan U.P. and downwind of Lake Ontario is likely to range
between 1-4".


...Mid-Atlantic...
Day 1...

The first winter hazards of the season for much of the Mid-
Atlantic is unfolding this morning. As weak low pressure slides
eastward over the Southeast, enhanced 290K isentropic ascent,
increasing 850-700mb WAA aloft, and strengthening low-level frontogenesis
is producing periods of snow from the central Appalachians and
Blue Ridge of WV/VA on east across the central/southern VA Piedmont
and across the DelMarVa Peninsula. Light snow is advancing as far
north as the Washington D.C./Baltimore metro areas, which is
may result in slick roads for the Friday AM commute. This will be
the first accumulating snow of the season, likely resulting in
hazardous travel conditions on untreated surfaces across much of
the Mid-Atlantic. Farther south, an icy overrunning setup looks to
unfold from the southern Appalachians on east across northern NC.
A wintry mix is likely to cause some minor ice accumulations on
roads, sidewalks, and vegetation Friday morning and could cause
travel delays. Snow should taper off by mid-afternoon with
lingering icy conditions across affected areas of the Mid-Atlantic
through Friday night.

Snowfall accumulations are likely to range between 1-4" from
southern WV and southwest VA across southern VA (including the
Richmond metro area) and into the lower DelMarVa Peninsula.
Localized totals >4" are possible in the Blue Ridge Mountains of
southwest VA. In terms of ice accumulations, most areas from the
VA/NC Blue Ridge on east across southern VA and northern NC can
expect minor accumulations less than a tenth of an inch, although
some of the southern Appalachians of NC could see localized amounts
approach one-tenth. The WSSI does depict Minor Impacts through
Friday afternoon for most areas referenced in this discussion with
some localized Moderate Impacts in the southern VA Piedmont.


...Pacific Northwest, Northern & Central Rockies...
Days 1-3...

A highly active storm track into the Northwest will usher in
copious amounts of Pacific moisture from the Pacific Northwest on
east into the Northern and Central Rockies. A steady barrage of

90th climatological percentile PWATs will stream across the

Pacific Northwest into the Great Basin and Rockies today, with
another round of >90th percentile PWATs arriving in the Pacific
Northwest on Sunday. Synoptic-scale forcing will be located over
the Northern Rockies today, then over the Central Rockies Friday
night into Saturday as a persistent NW-SE oriented 250mb jet
streak places its diffluent left exit region overhead. Snow levels
over the Pacific Northwest will dip as low as 3,000ft while the
Northern Rockies generally hover around 4,000ft. As height falls
transpire today over the Northwest and continue through Saturday,
snow levels will drop to as low as 2,000ft, although the heaviest
snowfall will be confined to elevations above 5,000ft in the
Bitterroots, Lewis Range, and Sawtooth, above 6,000ft in the
Tetons, Absaroka, Big Horns, Bear River, and Wasatch Ranges, and
above 7,000ft in the central WY/CO Rockies. Snow looks to taper off
across the Central Rockies by Saturday evening, but the next
atmospheric river will deliver another plume of Pacific moisture
across the Pacific Northwest and northern Rockies on Sunday.

WPC probabilities are impressive Day 1 and 2 across the higher
terrain from Glacier NP through Yellowstone NP including portions
of the Sawtooth/Salmon River ranges, Absarokas, terrain of NW WY,
northern Utah, and into the Park Range of CO. Here, WPC
probabilities Day 1 and 2 reach above 70% for 8+ inches, and Day 1
and Day 2 snowfall could be impressive above generally 6000 ft
where locally 1-2 feet is possible. Over the next few days, WPC
probabilities paint a wintry picture across many of the Northern
and Central Rockies, as well as the higher elevations of the
Cascades (above 5,000ft) with high chances (>70%) for additional snowfall totals >18" in all of these listed ranges and elevations through
Saturday. In fact, the higher elevations of the Lewis Range,
Bitterroots, and Tetons have moderate-to-high chances (50-80%) for
snowfall totals >24". Moderate to heavy snow continues into Day 3
over the WA Cascades and northern Rockies, though probabilities
suggest less snowfall compared to the more snowy stretches on
Friday and Saturday. The WSSI shows many areas of Minor and
Moderate Impacts across the Northern and Central Rockies,
including some locally Major Impacts. The Major Impact potential
areas (considerable disruptions; dangerous travel and widespread
closures) include areas along the Wasatch east of Salt Lake City
and the more remote areas of these Intermountain West ranges.
Residents in these mountain ranges should prepare for a multi-day
stretch of winter weather that results in difficult and treacherous
travel conditions.

...Northern Plains & Midwest...
Days 2-3...

The active pattern of Pacific moisture and disturbances traversing
the Northwest will result in at least one of these disturbances
reaching the Midwest late Friday night into Saturday. A slug of
rich Pacific moisture within the 700-300mb layer will advance
across the northern Great Plains and reach the Missouri River
Valley by Saturday. The synoptic-scale setup favors the development
of an 850mb low with sufficient 850-700mb FGEN and WAA to the north
and east of the 850mb low track to support a band of moderate-to-
heavy snow. The band of snow starts out Saturday morning across
the Dakotas, then heads for southern MN and northern IA by late
Saturday afternoon and evening, and begins to weaken in intensity
by early Sunday morning the snow reaches the Lower Great Lakes and
OH Valley.

The latest WPC probabilities have increased with this forecast,
now supporting probabilities of 50-70% for snowfall totals >4" for
locations that banding (mentioned above) is most likely across the
Midwest. However, given the favorable synoptic and mesoscale
processes at play, a band of >6" snowfall totals that cause travel
headaches for residents in the Midwest is very much on the table,
as evident in the low-to-moderate chances (20-50%) for snowfall
totals >6" over northern IA. Those in the Midwest should continue
to monitor the forecast closely as additional changes in the
placement and totals of the heaviest snowfall could still change
over the next 24 hours.

...Northeast...
Day 3...

There remains a good deal of uncertainty in the forecast
on Sunday with the GFS remaining aggressive in a more
amplified/phase solution compared to the ECMWF/CMC. The GFS is also
noticeably wetter than the GEFS over the Northeast. The ECMWF/CMC
camp shows a broader and less amplified 500mb trough over the Great
Lakes and southeast Canada, but enough 500mb PVA and lake-enhanced
snowfall bands are showing low chances (10-30%) for snowfall
totals >4" downwind of Lakes Erie and Ontario. Some minor impacts
to travel are possible as denoted by the WSSI-P showing low-to-
moderate chances (30-60%) for Minor Impacts on Sunday.

Mullinax




$$

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FOUS11 KWBC 052005
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
305 PM EST Fri Dec 5 2025

Valid 00Z Sat Dec 06 2025 - 00Z Tue Dec 09 2025


...Pacific Northwest, Northern & Central Rockies...
Days 1-3...

A highly active storm track with several significant atmospheric
rivers into the Northwest will usher in copious amounts of Pacific
moisture from the Pacific Northwest on east into the Northern and
Central Rockies the next few days. A steady barrage of >90th
climatological percentile PWATs will stream across the Pacific
Northwest into the Great Basin and Rockies through Saturday, with
another round of >90th percentile PWATs arriving in the Pacific
Northwest Sunday into Monday. Synoptic-scale forcing for ascent
will be aided by a persistent NW-SE oriented 250mb jet streak with
its diffluent left exit region overhead. Snow levels over the
Pacific Northwest will dip as low as 3,000ft while the Northern
Rockies generally hover around 4,000ft. As height falls occur over
the Northwest through Saturday, snow levels will drop to as low as
2,000ft. That being said, the heaviest snowfall will be confined to
elevations above 5,000ft in the Bitterroots, Lewis Range, and
Sawtooth, above 6,000ft in the Tetons, Absaroka, Big Horns, Bear
River, and Wasatch Ranges, and above 7,000ft in the central WY/CO
Rockies. Snow looks to taper off across the Central Rockies by
Saturday evening, but the next atmospheric river will deliver
another plume of Pacific moisture and another round of heavy
mountain snowfall across the Pacific Northwest and northern Rockies
Sunday into Monday.

WPC probabilities continue to be impressive on Day 1 across the
higher terrain from Glacier NP through Yellowstone NP including
portions of the Sawtooth/Salmon River ranges, Absarokas, terrain of
NW WY, northern Utah, and into the Park Range of CO. Here, WPC
probabilities reach above 70% for 8+ inches, with locally higher
amounts of 1-2 feet generally above 6000 ft. Over the next few
days, WPC probabilities paint a wintry picture across many of the
Northern and Central Rockies, as well as the higher elevations of
the Cascades (above 5,000ft) with high chances (>70%) for
additional snowfall totals >18" in all of these listed ranges and
elevations through Sunday. In fact, the higher elevations of the
Lewis Range, Bitterroots, and Tetons have moderate-to-high chances
(50-80%) for snowfall totals >24". Moderate to heavy snow continues
later into Days 2 and 3 over the WA Cascades and northern Rockies,
though probabilities suggest less snowfall compared to the more
snowy stretches tonight into Saturday. The WSSI shows many areas of
Minor and Moderate Impacts across the Northern and Central
Rockies, including some locally Major Impacts. The Major Impact
potential areas (considerable disruptions; dangerous travel and
widespread closures) include areas along the Wasatch east of Salt
Lake City and the more remote areas of these Intermountain West
ranges. Residents in these mountain ranges should prepare for a
multi-day stretch of winter weather that results in difficult and
treacherous travel conditions.

...Northern Plains & Midwest...
Days 1-2...

A fast-moving clipper system, aided by a slug of Pacific moisture
combined with strengthening low-level frontogenesis and warm
advection, will support a swath of moderate to heavy snow from the
northern Plains into the Midwest the next couple of days. The band
of snow first starts to develop across the Dakotas late tonight
into Saturday morning, then heads for southern MN and
northern/central IA as it intensifies late Saturday afternoon and
evening. The band then begins to weaken by early Sunday morning as
the snow reaches the Lower Great Lakes and OH Valley.

The latest WPC probabilities have increased with this forecast,
now supporting probabilities of 50-90% for snowfall totals >4" for
locations that banding (mentioned above) is most likely across the
Midwest. However, given the favorable synoptic and mesoscale
processes at play, a swath of heavier and more impactful snow still
remains on the table, as evident in the low-to-moderate chances
(30-50%) for snowfall totals >6" over northern/central IA. By
Sunday, low probabilities (10-40%) of >4" of snow extend into
southern Wisconsin and northern Illinois as the quick-moving wave
weakens on its track into the Lower Great Lakes and OH Valley.
Those in the Midwest should continue to monitor the forecast
closely as additional changes in the placement and totals of the
heaviest snowfall could still change over the next 24 hours.

...Great Lakes & Northeast...
Days 1-3...

Periodic mid/upper level impulses rotating within a broad cyclonic
flow pattern will continue to support rounds of light-to-moderate
lake effect snowfall across the upper Great Lakes through Monday. A
cold frontal passage Saturday into early Sunday morning
revitalizes LES bands over the Michigan U.P. and downwind of Lake
Ontario over the Tug Hill. Then, the fast-moving clipper from the
Midwest races across the Great Lakes and Northeast later Sunday
into Monday, bringing more lake effect snow and likely a period of
steadier synoptic snow to interior portions of the Northeast and
northern New England. The latest 12Z guidance continues to suggest
a fairly flat mid/upper level shortwave as it passes over the
region, which would limit snowfall potential. That said, it would
not be surprising to see models trend a bit more amplified and more
snowy in future model cycles, so continue to monitor the forecast
in the coming days.

WPC probabilities show overall low chances (10-40%) of >4" of snow
across portions of northern Michigan downwind of Lake Superior and
Lake Michigan Saturday into Sunday. Low chances (10-30%) of >4" of
snow then extend downwind of Lake Erie and Lake Ontario and across
parts of northern New England Sunday into Monday.


Miller/Mullinax







$$

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