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FOUS11 KWBC 102035
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
335 PM EST Wed Dec 10 2025

Valid 00Z Thu Dec 11 2025 - 00Z Sun Dec 14 2025


...Pacific Northwest through the Northern High Plains..
Days 1-3...

The strong Atmospheric River (AR) will start to wane over the
Cascades tonight with the last push of moisture onto the coast. The
upper jet will wobble a bit across southern BC but keep the
Northwest in mild conditions with snow levels 7000-9000ft to start
this evening. Through the day tomorrow, increased ridging over the
Northeastern Pacific will allow snow levels to slip a bit,
especially by Thursday evening as the precipitation intensity
decreases. WPC probabilities for at least 8 inches of snow are >50%
above about 5500ft. Much colder air will dive southward east of the
Divide across Montana setting up a significant snowfall by Friday.

Over the High Plains, warm advection atop a cold surface boundary
layer will support freezing rain from northeastern MT southeastward
through southwestern ND into central SD on Thursday. Model QPF
placement/axis and amounts continue to vary across the region but
trended up with the latest cycle. This introduced some moderate
probabilities (30-60%) of at least 0.10" of icing over north central
SD and northeastern MT/southwestern ND.

By Day 2, ridging will push the moisture plume into British Columbia
but also allow a strong surface cold front to rush southward east of
the Divide. With a continued moisture surge up and around the Pac NW
(albeit less than earlier in the period but still a quite
respectable >90th percentile PW and IVT), snow will expand and
strengthen over central/eastern MT as snow ratios rise as well.
Strong low/mid-level FGEN may support a heavier axis of snow from
central to southeastern MT. Snow will continue into Saturday but
lift northward as the jet wobbles back to the northeast, pushing the
snow into northeastern MT. By Saturday afternoon upper ridging will
finally push inland into the Northwest, yielding drier conditions
for the region. For the day 2-3 period, WPC probabilities of at
least 4 inches of snow are >50% over a large area of Montana east of
the Divide, from just east of Cut Bank through Havre, southward to
Billings, and eastward to southeastern MT/northwestern SD. Within
this region, WPC probabilities for at least 8 inches of snow are
>40% across central MT between Havre and Billings.


...Central Appalachians & Northeast...
Day 1...

As low pressure tracks into the St. Lawrence Valley tonight into
Thursday, the focus will shift from synoptically driven snowfall
across northern New England and interior portions of the Northeast
to lake effect snowfall downwind of the Great Lakes. Prior to this
transition, additional snowfall will be most notable across the
Adirondacks, Berkshires, Green, and White Mountains where WPC
probabilities for >6" are moderate to high (60-90%). Additionally,
strengthening northwesterly winds oriented perpendicular to the
central Appalachians will also result in significant upslope
snowfall through tonight and into Thursday morning. WPC
probabilities for >4" of snow is moderate to high (50-90%) across
portions of the higher terrain of WV and far western MD with
similar chances for >6".


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

Cold advection within cyclonic flow around the storm system
exiting the Northeast will result in several lake effect snow bands
which are likely to produce multiple rounds of moderate to heavy
snow the next few days. The most prominent bands will develop and
persist along the Chautauqua Ride and across the Tug Hill through
Thursday, with the band off of Lake Ontario lingering into Friday
as well. Lesser bands will also affect the eastern Michigan U.P.
and the northwest section of Michigan`s Mitten with WPC
probabilities of total snowfall >4" of 30-70% through Friday.
Meanwhile, the Tug Hill Plateau sports high chances (>70%) for
snowfall totals topping 8", with low to moderate chances (30-60%)
for >12" amounts. Moderate to high chances (40-80%) of >8" also
remain along the Chautauqua Ridge through Friday as well.

By Day 3, a renewed shot of CAA associated with a sharpening trough
and embedded vort max will support additional bands of lake effect
snow downwind of all the Great Lakes, but especially across
portions of the eastern U.P. of Michigan and the northwest portion
of lower Michigan. Here, WPC probabilities for snowfall >4"
increase to 50-90%, with 20-50% probabilities of >8" even outlined
across a small portion of the U.P of Michigan. Low to moderate
probabilities of additional snowfall >4" are also highlighted
downwind of Lake Erie and Lake Ontario.


...Midwest, Ohio Valley, & Central Appalachians...
Day 2...

Emanating from the Northern Rockies/High Plains system, northwest
flow will support a clipper system from the Midwest through the Ohio
Valley into the central Appalachians Thursday afternoon into Friday.
Models continued to struggle with the QPF axis (varying a couple
hundred miles northeast to southwest), with a preference toward the
global and AI models vs the hi-res models. Sufficient moisture
combined with modest forcing beneath the 140kt jet streaks and
within/along a low-level thermal gradient should yield several
inches of snow where SLRs are >12:1. Day 2 WPC probabilities of at
least 4 inches of snow are >30% along an axis from central IL to
northern/northeastern KY.


...Corn Belt to the Midwest...
Day 3...

Broad cyclonic flow over Hudson Bay/eastern Canada will carry
another shortwave around its southwestern periphery Friday night
into Saturday from the Plains through the Corn Belt to the Midwest.
This will yield yet another chance of light snow for the region on
the heels of the previous system. WPC probabilities for at least 4
inches of snow on Day 3 are low for now, generally 10-30%, from Iowa
through central IL.


Fracasso/Miller/Mullinax


$$