Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
253 AM EDT Mon Mar 24 2025

Valid 12Z Mon Mar 24 2025 - 12Z Thu Mar 27 2025


...Pacific/Interior Northwest to Northern Rockies...
Day 1...

Lingering moisture over the Northwest and northern Rockies atop
the upper ridge will slowly dissipate today, with very high snow
levels around 8000ft.


...West Coast...
Day 3...

Next Pacific system will start to bring in some moisture to
western WA/OR and NorCal. Snow levels will still be quite high --
10,000ft on Wednesday -- but dropping to around 5000ft by 12Z
Thursday, which still start to bring snow to some passes.


...Great Lakes/Northeast...
Days 1-2...

Mature winter storm over the Great Lakes this morning will
continue eastward through southern Ontario as a new triple point
low develops near the NY Bight this afternoon. Cold air at the
surface this morning will be slow to erode over the higher
elevations (Catskills, Berkshires/Greens, Worcester Hills, and
parts of Maine) as WAA-driven precip arrives this morning, favoring
some freezing rain amid a snow-to-rain changeover for areas south
of I-90. As the coastal low deepens, it will tend to hold in colder
air over northern New England and much of Maine, with marginal
temperatures toward the coast. This will make for a heavy/wet snow
of a few inches in NH to several inches over interior Maine as the
low pressure moves through the Gulf of Maine this evening. Snow
will end overnight associated with the area of low pressure, but
the large cyclonic circulation over the Great Lakes will sustain
some lake-effect snow today into Tuesday, especially over the
northern U.P. of Michigan, northwestern Lower Michigan, and into
the Tug Hill Plateau. WPC probabilities for at least 4 inches of
snow are >50% over the aforementioned lake-favored areas as well as
over northern NH (White Mountains) into Maine north of I-95 until
Bangor, then along 95 to the Canadian border.


...New England...
Day 3...

Vort max moving through the base of the upper trough over the
Great Lakes on Tuesday will move off the Mid-Atlantic coast and
turn the corner northeastward early Wednesday. Models have wavered
on how close to bring this system to eastern New England, but at
least some light precipitation is likely to affect at least areas
east of I-91. With marginal to somewhat sufficient cold air in
place, some light snow is likely for eastern New England before the
system races northeastward into Atlantic Canada Wednesday evening.
Some of the models were much more vigorous than others, but the
probability of at least 4 inches is still low (10-30%) from
northern NH into Maine.


For days 1-3, the probability of significant icing of at least
0.10" is less than 10 percent across the CONUS.


Fracasso