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FOUS11 KWBC 252111
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
411 PM EST Tue Nov 25 2025

Valid 00Z Wed Nov 26 2025 - 00Z Sat Nov 29 2025


...Significant winter storm/locally a Blizzard continues to impact
parts of the Upper Midwest/Great Lakes through Wednesday before
lake effect snow intensifies Wednesday night and lingers through
Thanksgiving and even 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
into Sunday...

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


...Upper Midwest/Great Lakes...
Days 1-3...

Potent developing low over eastern South Dakota this afternoon will
continue to deepen/strengthen as it tracks east over Wisconsin
tonight and the northern L.P. of Michigan Wednesday. The trough
around this low takes on a negative tilt tonight as the downstream
SWly jet intensifies and a strong pressure gradient with a 1032mb
high over ND by Wednesday morning allows for a strong and broad
wind field that will allow Blizzard conditions as indicated by the
Blizzard Warnings over the U.P. of MI and in northeast SD. A
TROWAL forms on the western side of the storm as warmer air wraps
northward and westward around the low which aids dynamic banding,
but also results in a more marginal thermal environment tonight
over the eastern U.P. and Wednesday over the northern L.P. However,
areas on the back side of the low will see rapid cooling that
allows for heavy snow banding and eventually LES.

The system continues to strengthen/deepen through Thursday night as
it pushes in to Quebec and becomes rather sprawling. Powerful northerly
to northwesterly flow will transition the lake- enhanced snow to
lake effect snow over northern WI into the U.P. tonight into
Wednesday where the 850-lake temperature difference will be >15C
(-10 to -13C at 850mb and a lake temperature around 5C). Lake
effect snow will break out for the L.P. of MI Wednesday afternoon
and off the eastern Great Lakes late Wednesday night. The threat
for single-band LES exists over northern MI Thursday/Thursday night
and the eastern Great Lakes Thursday. Expect 850mb temperatures of
<-10C over Lakes Erie/Ontario SSTs around +10C, allowing intense
lake bands to persist on WSW to W to WNW flow as the cyclone shifts
north of the region. Single banded snow will drop southward and
become more multi-banded downwind of Lake Erie but may retain a
stronger single band off Lake Ontario. Multi- banded snow will
persist across the Upper Great Lakes as well through early Friday.

For the rest of the synoptic event, Day 1 WPC probabilities for >8"
are 50-90% from the northern MN/WI border through northern WI and
the western/central U.P. with potential for two feet centered on
the Porcupine Mtns. Day 1 snow probs for >4" greater than 40%
extend northeast from the Twin Cities across north-central WI.
Considerable LES is expected after the surface low passes late
tonight through Wednesday with Day 2 snow probs for >12" 50 to 80%
for most of the U.P. the northern L.P. west from I-75 (as well as
30% south of Grand Rapids). For Day 2.5 the snow probs for >8" are
50-90% southeast of Lake Erie (including the Chautauqua Ridge into
northwest PA) and over the Tug Hill.


...Cascades through Northern Rockies...
Days 1-2...

A strong WNWly upper jet shifts across Washington State tonight
with sufficient Pacific Moisture for the Cascades (snow levels
around 4000ft rising to 5000ft) continuing for the Northern Rockies
into Wednesday where snow levels rise from 3000ft to 4000ft. Day 1
snow probs for >6" are 40-60% above these snow levels for the WA
Cascades, Bitterroots to the Absarokas.

High moisture plume ahead of the next wave tracks into Oregon
Wednesday with snow levels rising over 8000ft in OR Wednesday
afternoon with WA snow levels of 6000ft. Day 2 snow probs for >6"
are limited to the high WA Cascades.


...Glacier NP through Dakotas to Iowa...
Day 3...

...Increasing Winter Storm Threat Friday into/through the
Weekend...

The next winter storm to affect the central U.S. comes from a
Pacific shortwave low that crosses Washington State Thursday night
that combines with a shortwave trough that drops from the Canadian
Arctic Wednesday night, reaching Montana (and thus the connection
to the NW low) Thursday night. This combined longwave trough digs
across the northern Rockies Friday as lee-side surface cyclogenesis
occurs over eastern WY/CO. Confidence is increasing that a
resultant developing low pressure system then tracks east over the
central Plains Friday night with ample Gulf moisture allowing heavy
snow bands to set up across portions of the Midwest.

Of particular note for Thursday night/Friday is the Pacific
moisture combining with Gulf-sourced moisture with strong dynamics
ahead of the Pacific low (which opens Thursday night as the
northern stream trough approaches) allowing heavy snow bands to
develop over much of the MT Rockies and adjacent High Plains. Day
3 snow probabilities for >6" there are around 20% in a swath that
tracks just north over Great Falls with 40-80% values for any and
all terrain north of the Red Lodge portion of the Absarokas.

As the low develops Friday, a deformation axis of snow develops
across South Dakota and stretches into Iowa by 00Z Saturday. Day 3
snow probs for >4" are currently limited to 10-40% mainly in
eastern SD, but it`s that banding that further develops and pivots
over the Midwest for much of Saturday.



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

Jackson


...Winter Storm Key Messages are in effect for the ongoing system
over the Upper Midwest and Great Lakes (link one below) and new
Key Messages are in production for the next wave (link two below) that
reaches the Northern Plains Thursday night and crosses the Great
Lakes through Sunday...

https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_1.png

https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_2.png



$$