Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
320 AM EST Mon Mar 01 2021

Valid 12Z Mon Mar 01 2021 - 12Z Thu Mar 04 2021

...Northern Great Lakes through the Northeast...
Days 1-2...

A closed 500mb low moving across Ontario this morning will shift
E/SE across Maine this evening and then into the Canadian
Maritimes tonight. Ahead of this feature, deep SW flow and
associated WAA will spread moisture northward across New England
through tonight. While the column is marginally cold enough early
for some rain/snow mix or even some light freezing rain/sleet, in
general most of the area will receive rain. The exception is
likely to be far northern Maine where a colder column and more
robust ascent will allow for a period of moderate to heavy
snowfall. WPC probabilities for 4 inches are as high as 70%, but
confined north of I-95.

This same trough will drive an arctic cold front across the Great
Lakes and New England through tonight as well. Behind this front,
strong CAA will produce periods of LES in the favored NW snow
belts of the U.P. of MI and east of Lake Erie. While duration and
intensity is modest, briefly heavy snow with rates greater than
1"/hr are likely in the eastern U.P. where the best forcing
directly intersects the DGZ, and WPC probabilities are as high as
50% for 4 inches. East of Lake Erie, some channeled moisture from
Lake Huron may enhance snowfall south of Buffalo, NY, but WPC
probabilities for 4 inches are less than 5%. In addition to this
LES, it still looks likely that intense snow squalls will race
across Upstate New York, northern Pennsylvania, and parts of New
England this evening and tonight. While accumulations from these
squalls should be minimal, briefly intense snowfall rates of more
than 1"/hr and strong winds could whiten the ground and produce
significantly reduced visibility.


For Days 1-3, the probability of significant icing (0.25-inch or
greater) is less than 10 percent.

Weiss