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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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