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

Valid 00Z Thu Feb 27 2025 - 00Z Sun Mar 02 2025


...Northeast...
Days 1-2...

The first in a series of progressive shortwaves to impact the
Northeast with wintry weather over the next few days will pivot
southeast from the Upper Midwest tonight, reaching the Great Lakes
before 12Z Thursday and then pushing east of 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 the PA-NY line
into New England, but changeover to a mix and then rain across all
but the higher terrain of the Adirondacks, Whites, and northern
Maine. WPC probabilities for 4+ inches of snow through Thursday
evening are medium (50-70%) along the White Mts of NH and ME, with
lower probs (10-20%) stretching eastward to just northwest of
Portland. Chances for ice accretion over 0.1" are low outside of
the Catskills, but a glaze of freezing rain is possible across the
favorable elevated sections of New England.

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 into
early Friday, 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.


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

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 York State. WPC
probabilities D3 are high (>70%) for 4+ inches in these regions,
with lower probs (10-30%) situated across northern New England on
D3 outside of the elevated Green and White Mts. The greatest
potential for at least 8 inches of snow (40-60%) exists along a
WNW-ESE swath from the MN Arrowhead to the eastern U.P. (including
the Keweenaw Peninsula).

Snell/Weiss