725
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




$$