423
FOUS11 KWBC 241905
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
205 PM EST Mon Nov 24 2025

Valid 00Z Tue Nov 25 2025 - 00Z Fri Nov 28 2025


...Significant winter storm to impact parts of the Northern Plains
and Upper Midwest/Great Lakes through Wednesday before lake effect
snow intensifies on Thanksgiving. Key Messages have been issued for
this storm...


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

Shortwave trough exiting the Northern Rockies this afternoon will
move into the northern High Plains tonight. The upper jet across
the US/Canada will sharpen and support a strengthening area of low
pressure that will move from the Plains to the Upper Midwest and
western Great Lakes over the next few days. Tonight, an 850mb low
will form along a strengthening 925-850mb front over central ND,
while a narrow inverted trough axis forms on its western flank. By
12Z Tuesday, bands of moderate to heavy snow are likely from
northeastern MT to central ND with increasingly gusty winds as the
low pressure strengthens. Tuesday afternoon the low over
southeastern MN will start to deepen even more rapidly as the mid-
level shortwave starts to close off, allowing a TROWAL to form on
the western side of the storm. This could allow for >1"/hr snowfall
rates along with gusty winds over 30mph, causing some blowing/drifting
snow. Some areas closer to Lake Superior and over central MN will
see marginal temperatures and snow may not accumulate quickly if
the rates are not high, though colder air will eventually win and
change all areas to snow overnight into early Wednesday as the low
moves into the U.P. of Michigan and deepens into the mid 990s mb.
There remains some latitudinal uncertainty with today`s guidance
shifting slightly south across the ND/MN and aligned with the
second ensemble cluster in WPC`s QPF cluster prototype in the
north-central U.S.. Mesoscale banding within the inverted trough
and eventual TROWAL will likely make for rapidly changing
conditions within narrow corridors of heavy snow.

By Wednesday night into early Thursday, the system will reach its
peak intensity over Ontario and take the bulk of its snow with it.
However, northerly to northwesterly flow will transition the lake-
enhanced snow to lake effect snow over northern WI into the U.P.
where the 850-lake temperature difference will be >15C (-10 to
-14C at 850mb and a lake temperature around 5C). Lake effect snow
will eventually break out across the rest of the Great Lakes by
Thursday morning and continue into the medium range period.

WPC probabilities for at least 8 inches of snow are 30-50% from
northwestern ND to central MN. Then, these probs increase to 50-70%
across northeast MN and the MN Arrowhead. Across northern WI and
into the U.P., the combination of synoptic snow and then lake
effect snow will boost totals well over a foot. There, WPC
probabilities for at least 24 inches of snow are 50-80% from near
Ironwood northeastward across the northern portion of the U.P. near
the Huron Mountains. This region is also where major impacts due to
snow amounts are possible. Residents and visitors in the Upper
Midwest/Great Lakes are advised to check the latest forecast
before traveling this week.


...Great Lakes...
Day 3...

Lake effect snow will continue on day 3 (00z 11/27-00z 11/28) as
the deep low drifts into southeast Canada and promotes strong
west-northwesterly flow over the relatively warm lake waters. Fetch
will be favorable for additional snow across the U.P. of MI and the
northern L.P., as well as along the shores of Lake Erie from
northwest PA to western NY as well as the Tug Hill of NY downwind
of Lake Ontario. Current WPC probabilities for at least 8 inches of
snow on day 3 are 60-80% for these locations.

...Pacific Northwest/Northern Rockies...
Days 1-3...

The next Pacific system moves into western WA on Tuesday at the
nose of an 140kt 250mb jet. Colder air in place ahead of the
moisture may support some spotty freezing rain along the leeward
slopes/valleys of the Cascades and in the valleys of the Columbia
River Basin over northern WA. Snow levels will gradually rise as
the warm front lifts through Tuesday night into early Wednesday,
but the surface front will takes longer to cross the Cascades
rather than the more robust 700mb WAA nose that support the
potential for icy conditions east of the Cascades. Thanks to a
longwave trough firmly entrenched over the North Pacific, an
extended moisture fetch into the the Pacific Northwest will support
a more or less continuous stretch of mountain snow over the
Cascades and downstream into the Northern Rockies through the end
of this forecast period (then continuing into the medium range).
Snow levels will vary, starting around 2000-4000ft then rising to
around 5000-7000ft as milder air moves in ahead of a potent low
pressure system on Thursday. WPC probabilities for at least 8
inches of snow are >50% above about 5000ft. Both Snoqualmie and
Stevens Pass may see multiple inches of snow before snow levels
rise above the passes early Wednesday.


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

Snell


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

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



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