FOUS11 KWBC 130719
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
219 AM EST Mon Jan 13 2025

Valid 12Z Mon Jan 13 2025 - 12Z Thu Jan 16 2025

...Northern Rockies/Western High Plains...
Day 1...

Weak shortwave diving through central/eastern MT this morning will
sink southward through WY atop a surface boundary over eastern MT
into the Black Hills, supporting generally light snow with some
terrain enhancement. Areas in the Black Hills have a high chance
(>70%) of at least 4 inches of snow today.


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

Occluded area of low pressure over Lake Superior this morning will
only slowly move to the east, leaving a surface trough across the
region and NW flow into the U.P. of Michigan. Additional height
falls via a cold closed low moving out of Canada into northern MN
will maintain/invigorate cyclonic flow across all the Great Lakes
behind the cold front moving into New England. Lake effect snow
will pick up in earnest over the eastern Great Lakes and maintain
itself over Lake Superior into the U.P. and northwest Lower MI for
the next 2-3 days. Snow will gradually wind down from NW to SE late
D2 into D3 ahead of a Canadian system.

For the period, WPC probabilities of at least 8 inches of snow are
>50% over the Keweenaw Peninsula and over the eastern U.P. on NW
flow, as well as into northwestern Lower MI. East of Lake Erie, WPC
probabilities for at least 8 inches of snow are >50% from Erie, PA
through the Chautauqua Ridge to near the Buffalo southtowns with
some totals likely over a foot. East of Lake Ontario, snowfall will
maximize into the Tug Hill Plateau where WPC probabilities for at
least 12 inches of snow are high (>70%) and even have a small area
of >50% probs for at least two feet around Redfield.


...PA/NY...
Days 1-2...

Approaching cold front today may instigate some snow squalls
across the region given relatively steep low-level lapse rates. On
Tuesday, approaching vort max may again provide an atmosphere
conducive for some snow squalls, with the models generally showing
an area of >1 in the snow squall parameter. Amounts will generally
be light but these can be hazardous to drivers.


For the Day 1-3 period, the probability of significant icing of at
least 0.10" is less than 10 percent across the CONUS.


Fracasso

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