FOUS11 KWBC 230705
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
305 AM EDT Sun Mar 23 2025

Valid 12Z Sun Mar 23 2025 - 12Z Wed Mar 26 2025


...Pacific/Interior Northwest to Central Rockies...
Days 1-2...

Upper ridging just off the Pac NW coast this morning will continue
to build into the region, pushing snow levels that are around
3500-5000ft at 12Z to well over 6000-8000ft by 00Z over the
Cascades. Farther east over northern ID into MT, snow levels will
still rise today confining much of the accumulating snow to levels
above 5000ft (>6 inch amounts). Into Monday (D2), moisture will
persist into WA and the northern Rockies but with very high snow
levels above 8000ft. Heights will build into Tuesday, essentially
ending any precipitation in the Northwest altogether.

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

Mid-level shortwave over the Dakotas this morning will move
eastward today into the Upper Midwest as it surface low pressure
center follows suit across central MN into northern WI. By this
evening, the triple point low will start to become the dominant
center (near Green Bay) and move eastward across northern Lower
Michigan and then into southern Ontario as the cold front bows out
through the Northeast early Monday. With an amplifying upper
pattern, this will slow the progression of the system out of the
region, allowing cyclonic flow to persist over the Great Lakes into
the Northeast into Tuesday, favoring lake-effect snow with 850
temperatures < -10C. Though fairly progressive to start, the system
will still yield significant snow for portions of the eastern
Arrowhead and into the U.P. of Michigan via wraparound/convergent
snow in the deformation band on the NW side of the sfc low, WAA-
driven snow ahead of the sfc low (northern WI into the U.P.), or
both over northern/northwester Lower Michigan via the triple point
low. Over the Northeast, south of the eventual track of the surface
low, WAA will drive much of the precipitation on Monday with some
icing at the onset in colder areas turning over to rain and snow
farther north toward the Canadian border where it will take longer
to warm up toward freezing -- and some areas will not as a result
of a new triple point low over the Gulf of Maine, acting to hold
colder air in over northern NH and northwestern ME. Finally, some
lake effect snow will affect the Tug Hill Plateau Tuesday with
lighter upslope snow to the south into the central Appalachians.
Snowfall will finally wind down by early Wednesday (end of this
forecast period).

For the three-day period, WPC probabilities of at least 4 inches
of snow are highest (>50%) over northeastern MN, northern WI, the
U.P. of Michigan, northern/northwestern Lower MI, and in the Tug
Hill Plateau region including some of the Adirondacks. Some areas
of the White Mountains may see in excess of 4 inches of snow as
well. The heaviest snow may fall over far northeastern MN where
local convergence off Lake Superior will add to the snow efficiency
(in addition to higher SLRs in the colder air). There, WPC
probabilities of at least 8 inches of snow are > 70%.


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


Fracasso


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