FOUS11 KWBC 200909
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
409 AM EST Tue Jan 20 2026

Valid 12Z Tue Jan 20 2026 - 12Z Fri Jan 23 2026

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

Sprawling Hudson Bay vortex dominates the continental pattern
through this week. A pair of shortwave troughs round the low,
emerging from the Canadian Prairies as clippers and cross the
Northern Plains/Upper Midwest and the Great Lakes today and
Wednesday. These clippers will continue to trigger LES bands over
the typical snow belts in their wake.

The first shortwave trough axis reaches Montana this morning with
repeating areas of moderate snow through the morning with
topographical enhancements where 1"/hr snow rates are possible. Day
1 PWPF for >4" are around 50% on the Little Belt and Big Snowy Mtns.

This clipper will redevelop snow bands over eastern SD this
afternoon with a decent, but narrow swath of snow then east along
the MN/IA and WI/IL borders tonight and southern MI late tonight
into Wednesday. Day 1.5 PWPF for >4" is 40-50% from northeast IA
along the WI/IL border and southwest MI. The Wednesday clipper
should follow a similar track, but with lower overall precip.

The Great Lakes ice coverage is rising, currently around 18%
mainly on narrower bays and western Lake Erie per GLERL.
Sufficiently steep low level lapse rates persist with 850mb
temperatures of -20C to -25C over surface water temperatures
between +1C and +5C.

Westerly flow continues today ahead of the first clipper with a
lull spreading east tonight through Wednesday night as the two
clippers cross. The strong single-banding persists from Lake
Ontario today with Day 1 PWPF for >8" additional after 12Z over 80%
in the Tug Hill Plateau. Day 2 PWPF for >6" is around 30% east of
Lake Erie and around 50% in the Tug Hill. Then LES resumes for the
northern Lakes with Day 3 PWPF for >6" over 90% in the Tug Hill.

...Southern Tier... Starting Day 3...

Southern stream low pressure pushes inland over the northern Baja
California Friday with broad cyclonic flow out ahead which opens up
Gulf moisture to surge over Arctic-sourced air spilling down the
Plains from the Hudson Bay vortex. Broad areas of heavy wintry
precip are expected to develop on Friday over Texas to the
Southeast. Confidence is high for this event occurring though
details on how much winter accumulations, types, and locations have
uncertainty mainly derived from the timing of the southern stream
wave surging inland. Key Messages on this storm and the extreme
cold are active and linked below.

Jackson

...Extreme Cold Key Messages and Southern Tier Winter Storm Key
Messages are linked below...

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

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

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