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FOUS11 KWBC 300711
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
211 AM EST Tue Dec 30 2025

Valid 12Z Tue Dec 30 2025 - 12Z Fri Jan 02 2026


...Great Lakes, Central Appalachians, Interior Northeast...
Days 1-3... Maximum impact level from WSSI: Moderate to Major

Deep upper troughing will linger over southern Hudson Bay/James
Bay for the next few days, maintaining broad cyclonic flow out of
central Canada and across the Great Lakes. This will result in a
mostly continuous period of lake effect snow downwind of all Great
Lakes but focused especially east of Lakes Erie and Ontario. Two
mid-level shortwaves will zip through the southwest/southern base
of the trough which will act to disrupt the banding and also infuse
a bit more lift and moisture to the region. With lake temperatures
in the 30s to 40s and 850mb temperatures -15 to -20C, sufficient
lift will be generated over the lakes on a general NW to W flow
from the Upper Lakes to Lower Lakes, respectively. This will set up
multi-banded snows over Michigan with multi to strong single
banded snows over NW PA, western NY, and between Syracuse and
Watertown. The bands will modulate due to the shortwaves moving
through the region, with the first tonight and the second Wednesday
with perhaps a third weaken one overnight Thursday. The passage of
the second shortwave and associated surface arctic front may also
bring the threat for snow squalls tomorrow afternoon into the
overnight (New Year's Eve) from Michigan to Ohio to Pennsylvania
per the Snow Squall Parameter.

In addition to the lake effect snows, strong upslope ascent into
the central Appalachians will favor at least modest totals over
eastern WV northward through western MD and into the Laurel
Highlands in PA, especially Wednesday into Thursday.

WPC's 72-hour snowfall probabilities show high chances (>70%) for
snowfall totals >18" in NW PA and along the Chautauqua Ridge in
southwestern NY into some of the Buffalo Southtowns. Localized
amounts could exceed 2-3ft. Just east of Lake Ontario, WPC
probabilities show moderate-to-high chances (50-70%) for snowfall
totals >18" in the region between Syracuse, Watertown, and east of
Rochester (centered around Oswego). Over Michigan, totals will
likely be lower, but still appreciable. WPC probabilities for at
least 8 inches of snow are highest (>50%) near/southwest of the
Keweenaw Peninsula, the eastern U.P., and over northwestern Lower
Michigan. Farther south, WPC probabilities for at least 8 inches of
snow are highest over eastern WV northward to the Laurel Highlands
in PA. Light to perhaps modest snow is also possible into the
Green Mountains in VT via upslope flow.


...Sierra Nevada to the Central Rockies...
Days 2-3... Maximum impact level from WSSI: Minor to Moderate

A deep trough in the subtropical Eastern Pacific will lift toward
California and weaken on Wednesday, spreading generally light to
moderate QPF over the region. Snow levels will be high
(>9000-10,000ft) where more than 8 inches is likely above 10,000ft
through Thursday night. Lighter precipitation will spread
northwestward through Utah to the CO Rockies amid high snow levels
(8000-9000ft) and generally near to under 6 inches of snow.


Fracasso


$$

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