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QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
236 AM EDT Wed Mar 26 2025

Valid 12Z Wed Mar 26 2025 - 12Z Sat Mar 29 2025


...Northeast...
Day 1...

Compact upper low over southwestern Ontario this morning will move
across northern NY/VT midday and through Maine this evening. This
will spur some more light snow into the Tug Hill Plateau where 1-3"
is likely. Farther east, low probabilities (10-30%) are shown for
more than 4 inches of snow over the Green and White mountains via
upslope enhancement as the feature moves through.



...Upper Midwest/Great Lakes/Northeast...
Days 2-3...

Flattening upper ridging exiting the High Plains Thursday combined
with lee-side surface cyclogenesis centered over South Dakota
Thursday night will favor broad WAA-driven precipitation along and
north of a surface boundary astride the Upper Midwest into the
Great Lakes. With the fast zonal/progressive flow, this will
quickly expand eastward through Canada and into the Northeast with
an influx of moisture from the southwest, reaching into NY Fri
evening then into New England overnight into early Saturday.
Temperatures are marginal for most areas, confining wintry
precipitation to areas closer to the Canadian border. However, that
sub-freezing surface layer will be overrun from the S/SW with
warmer air aloft, promoting a rather large area of sleet/freezing
rain from northern MN eastward across the U.P. of Michigan and
northern WI across Ontario and into the Adirondacks. Ptype from the
models (and NBM) show a strong signal for freezing rain
(impressive for late March), but this may be modulated my afternoon
insolation. Nevertheless, WPC probabilities for at least 0.10"
icing are moderate (30-70%) over northeastern MN, the U.P./northern
WI, and the northern part of Lower Michigan. Snow amounts may be
limited, with the highest amounts of a couple inches over northern
MN where WPC probabilities for at least 4 inches are barely 10%.


...Cascades into the northern Sierra Nevada...
Days 2-3...

An anomalously deep, cold core low in the northeast Pacific will
curl up toward Vancouver Island as its wound up occlude front moves
inland tonight. High snow levels (>8000ft) this afternoon will
steadily drop to around 4000-5000ft tomorrow, then to around 4000ft
Friday with the passage of the upper trough. Snow will eventually
get to some of the passes but much of this will fall over the
higher terrain. Two-day probabilities of at least 8 inches of snow
are highest above 5000ft or so along the Cascades southward to the
NorCal ranges and northern Sierra. Moisture will continue inland to
the northern Rockies with a few to several inches of snow for the
Blue Mountains and into SW MT as a frontal boundary in the area
acts as another focus for forcing. There, WPC probabilities for at
least 8 inches of snow are low (10-30%).


Fracasso


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