Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
205 PM EST Sat Jan 11 2025

Valid 00Z Sun Jan 12 2025 - 00Z Wed Jan 15 2025

...Northern/Central Rockies to the Upper Midwest & Great Lakes...
Days 1-3...

A positively-tilted upper-level trough will promote healthy upper
level divergence over the Upper Midwest today and into tonight,
providing a supportive environment for an Alberta Clipper tracking
east towards the Upper Great Lakes by Sunday. On the backside of
Clipper, modest 700-300mb moisture aloft combined with upslope
flow in wake of a cold frontal passage will lead to periods of
heavy mountains snow in the Little Belt, Big Snowy, Absaroka, Big
Horns, and Black Hills through Sunday afternoon. WPC probabilities
show high chances (>70%) for snowfall totals above 8" in the
higher terrain of these mountain ranges. The Little Belt, Big
Snowy, and Big Horns in particular are forecast to receive over 2
feet of snow by the end of the weekend.

As the Clipper moves east this afternoon, 850-700mb WAA ahead of
the system will provide modest lift and moisture aloft to support
periods of snow from the Red River of the North on east to the
Minnesota Arrowhead. Some lake enhancement of these snow bands is
expected along the MN Arrowhead tonight and into Sunday morning.
WPC
probabilities show moderate-to-high chances (50-70%) for snowfall
>4" along the entire MN Arrowhead coast, with the northern-most
section of the Arrowhead even having moderate chances (40-60%) for
snowfall totals >8". By Sunday evening the Clipper will be tracking
over Lake Superior and CAA on the backside of the storm will
reinvigorate LES bands from northern Wisconsin on east across the
Michigan U.P.. The clipper system stalls out and occludes over the
eastern portion of Lake Superior Sunday night, allowing for the
TROWAL to be placed over Lake Superior and along the northern coast
of the Michigan U.P. through Monday. Heavy snow will unfold from
the Huron Mountains and Keweenaw Peninsula to as far south as the
Traverse City area of northwest Michigan through Tuesday. WPC
probabilities show high chances (>70%) for snowfall totals >8" in
these areas with the Hurons sporting low chances (10-30%) for
totals >12" through Tuesday afternoon.

Farther east, the cold front tracking across the Great Lakes
prompts a burst of CAA amidst WSW flow over Lakes Michigan, Erie,
and Ontario. Guidance is keying in on he development of a couple
LES bands forming off Lakes Erie and Ontario Monday night that
last through Tuesday. This is likely to cause periods of heavy snow
(hourly rates of 1-2"/hr) in parts of northwest PA and western NY
along the Chautauqua Ridge and over the Tug Hill Plateau. Through
00Z Wednesday, WPC probabilities show moderate-to-high chances
(50-70%) for snowfall totals >6" in these areas. Expect both the
probabilities and snowfall totals in subsequent forecast
discussions to reference higher amounts as periods of heavy
snowfall are likely to continue into Tuesday night and through
Wednesday morning.


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


Mullinax