Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
212 PM EST Fri Feb 28 2025

Valid 00Z Sat Mar 01 2025 - 00Z Tue Mar 04 2025


...Great Lakes through the Northeast...
Day 1...

An unusually strong clipper system (MSLP below the 0.5
climatological percentile per the NAEFS) swinging across the Upper
Great Lakes this afternoon will track eastward just to the north of
New England on Saturday. Modest WAA ahead of the storm will allow
for a period of moderate snowfall across northern New England, Tug
Hill, and northern Adirondacks tonight before mid-level dry air
and warming of the column quickly ends any widespread snowfall by
Saturday afternoon. Then, on the backside of the system, beginning
first throughout the Upper Great Lakes this evening, CAA increases
and drives up chances for renewed lake-effect snow and eventually
favorable upslope conditions from the central Appalachians to
northern New England. Additionally, as the CAA peaks along the East
Coast on Saturday and low-level lapse rates increase with diurnal
heating during the afternoon hours, snow showers and localized snow
squalls are possible from the eastern Ohio Valley through New
England. WPC probabilities show high chances (70-90%) for snowfall
totals >4" across the Tug Hill Plateau and northern Adirondacks of
New York, as well as the Green and White Mountains, plus parts of
far northern Maine. Lake-effect snow downwind of Lake Superior have
also prompted medium probabilities (40-60%) of an additional >4"
of snow throughout parts of the Michigan U.P.


...California & Great Basin...
Days 2-3...

A closed upper-low approaching California on Sunday will direct an
IVT that is topping out not much higher than 250 kg/m/s at the
Sierra Nevada and Southern California ranges. 850mb and 700mb winds
topping the 90th climatological percentile (per NAEFS) may aid in
some modest upslope flow, but this IVT is not particularly strong,
which should limit most heavy amounts to the highest/more remote
elevations. Snow levels will be as low as 4,000ft from the Sierra
Nevada on east into the Great Basin, but the heavier amounts will
generally be confined to elevations above 6,000ft. Snow will fall
heaviest over the Sierra Nevada and as far north as the
Shasta/Siskiyou Sunday afternoon and into Sunday night. As the
upper low approaches Sunday night, Pacific moisture will spill over
into the Great Basin with moderate-to-heavy snowfall along the
ridge lines of central Nevada Sunday night and into Monday.
Moisture and a potent upper low will then eventually reach the
central Rockies late Monday. WPC probabilities depict moderate-
to- high chances (50-80%) for snowfall >8" at elevations above
7,000ft in the Sierra Nevada through Monday morning. Similar
moderate-to- high chance probabilities for >4" of snowfall exist
along the ridges of central Nevada and Utah ranges through Monday
evening.


Snell/Mullinax