FOUS11 KWBC 070855
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
355 AM EST Fri Mar 7 2025

Valid 12Z Fri Mar 07 2025 - 12Z Mon Mar 10 2025

...New York/New England...
Days 1-3...

Negatively tilted longwave trough over New England will lift north
over the Canadian Maritimes today as the surface low continues to
develop on its transit of the Gulf of St. Lawrence. Heavy snow on
the back side of this surface low under the upper trough will
continue over eastern/northern Maine this morning where Day 1 PWPF
for >6" is 50-80%.

WNW flow off Lake Ontario will continue to allow lake effect snow
(LES) over Upstate NY today with upslope snow over the Adirondacks,
northern Greens, and Whites. Day 1 PWPF for >4" are 20-40% over the
southern Tug Hill down through Syracuse and Utica as well as over
the Presidential Range in NH (which are repeated for Day 2 on
continued upslope flow).

A northern Alberta Clipper tracks over Ontario on Sunday, reaching
northern NY/New England Sunday night. Day 3 PWPF for >4" is around
20% for the northwest facing Adirondacks.


...Central Plains through the Midwest to the North-Central Appalachians...
Day 1...

The leading shortwave trough from Low pressure over the West is now
over northeast CO and will eject east through the Midwest today on
a strengthening WSWly jet. Robust, but narrow banding continues
across northern Neb/IA early this morning, and shifts east over
Chicago this afternoon. However, the wave is being sheared and the
surface low is filling, so the banding intensity should continue to
wane as it tracks east. Sufficient overlap of synoptic ascent
through the left-exit of the jet streak aloft, 850-600mb
frontogenesis, and ample Gulf-sourced moisture will continue to
drive the snow bands that should see rates drop to moderate by
mid-morning. PWPF for additional snow >2" after 12Z are 30-60% from
northeast Neb across north-central IA and along the IL/WI border.
Snow tonight reaches western PA and the central Appalachians where
there are 20-40% PWPF for >2".


...Four Corners States through Oklahoma/Texas Panhandles...
Days 1-2...

A closed low over over the southern CA border is at the base of the
still positively-tilted trough over the West. This low tracks over
southern AZ today and NM tonight before moving over the TX
Panhandle on Saturday. Further reinforcing troughs will slow the
progress east and prolong the snow fall over AZ terrain today and
the southern Rockies onto the southern High Plains tonight into
Saturday. Snow levels hover in the 4000-5000 ft range over the
Southwest, but start around 6000ft this evening over the I-25
corridor near the CO/NM border/Raton Mesa. Day 1 PWPF for >8" are
50-90% along the Mogollon Rim/White Mtns, and over the southern San
Juans/Sangre de Cristos including the Raton Mesa.

Decent dynamics make for snow levels around 3500ft in the TX
Panhandle in banding on the north side of the sfc low. Snow
probabilities have risen here with Day 1.5 PWPF for >4" 40-70%
over the TX/OK Panhandles and over 80% in northeast NM.


...Western Washington...
Days 2-3...

A hearty plume of Pacific moisture tracks into western WA ahead of
the next low dropping south from the Gulf of Alaska Saturday
through Sunday night. Snow levels are generally around 4000ft
through Sunday in the WA Cascades before dropping to 2000ft Sunday
night under the trough axis. Day 2.5 PWPF for >6" is limited to the
highest Olympics/northern WA Cascades, but the Day 3 drops down to
pass level with greater coverage of >40% probabilities.


Jackson

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