FOUS11 KWBC 260711
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
211 AM EST Wed Feb 26 2025

Valid 12Z Wed Feb 26 2025 - 12Z Sat Mar 01 2025

...Upper Great Lakes through the Northeast...
Days 2-3...

A series of shortwave troughs moving through the flow this week
will result in an amplified longwave trough deepening across the
eastern CONUS. This will create period of active wintry weather
from the Upper Great Lakes through northern New England.

The first of these shortwaves will pivot southeast from the Upper
Midwest Wednesday night, reaching the Great Lakes before 12Z
Thursday and then pushing into New England on Friday. This will
sharpen the associated longwave trough across the east, driving a
cold front across the region, which will be draped from a wave of
low pressure likely developing downstream of the lead shortwave. As
this low moves E/NE from Michigan to New England, accompanying WAA
will help spread precipitation northeastward as PWs surge to +1 to
+2 sigma according to NAEFS ensemble tables. The surface low
tracking across northern New England will allow precipitation to
start as snow in many places from Upstate New York into New
England, but changeover to a mix and then rain across all but the
higher terrain of the Adirondacks, Whites, and northern Maine.

Then as the subsequent cold front pushes through on Thursday,
upslope flow in a still moist column will drive periods of moderate
snowfall across the Adirondacks, Greens, and Tug Hill Plateau, the
latter aided by lake Ontario moisture enhancement. This will
result in locally heavy snow exceeding 4 inches as reflected by WPC
probabilities D2 that are moderate to high (30-70%) across these
mountain ranges, with locally 6+ inches possible in the higher
terrain and across the Tug Hill Plateau.

A subsequent shortwave will race southeast immediately on the heels
of this first system, pushing an Alberta Clipper type low from
northern MN early Friday to New England Saturday. This system will
be compact and progressive, but a strengthening shortwave and
favorable positioning of an upper level jet streak will produce
significant ascent to spread moderate to heavy precipitation across
the region. Although this system will Alas be progressive, a
region of overlapping frontogenesis and deformation north of the
surface low will result in an axis of heavier precipitation, and
since the column will be quite cold behind Thursday's cold front,
this will produce a swath of heavy snow from the Arrowhead of MN,
across the U.P. of MI, eastward into northern New England. WPC
probabilities D3 are high (>70%) for 4+ inches from the eastern
U.P. through the far northern portion of the L.P., with 30-70%
chances for 4+ inches encompassing that region as far west as the
tip of the Arrowhead to as far east as the western Adirondacks.

Weiss


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