Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
244 AM EDT Tue Mar 25 2025

Valid 12Z Tue Mar 25 2025 - 12Z Fri Mar 28 2025


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

In the wake of the departing system just leaving the Northeast
this morning, broad cyclonic flow centered south of Hudson Bay will
maintain a cold flow of air over the slowly warming Great Lakes,
promoting some lake effect snow for the next couple of days. The
most favored areas will be across portions of the eastern U.P. of
Michigan in any more organized/persistent bands, east of Lake
Ontario along the long fetch of the lake (Tug Hill Plateau), and
into the Green Mountains via upslope enhancement. Two-day totals
will be generally light (1-3") but the aforementioned areas show
the highest probabilities of seeing at least 4 inches of snow
(10-70%, with the highest probabilities of at least 6 inches over
the Tug Hill).


...West Coast...
Days 2-3...

An anomalously deep and impressively wound-up system in the
northeast Pacific late Tue into Wed will start to field moisture
into the West Coast starting Wednesday afternoon. Strong ridging
over the West means snow levels will start very high (>8000ft)
during the middle of day 2 (00Z Thu) but will trend lower into day
3. Then (12Z Thu - 12Z Fri) the upper/sfc low will curl
northeastward to northward to a position just offshore Vancouver
Island, allowing its long occluded front to push inland. This will
take snow levels down to about 5000ft by 12Z Fri over the Cascades
into the far northern NorCal ranges and about 6000-7000ft over the
northern Sierra as a 130kt jet streak moves through. QPF amounts
will be light to modest inland with heavier amounts along the coast
and into the Olympics in WA. Rain will change to snow with low
SLRs and will come in a couple waves -- initially with the front in
the higher PW plume and then with the upper trough. Snow will
accumulate the most at the highest peaks but eventually will get to
some high passes in northern CA. Through 12Z Fri, WPC
probabilities for at least 8 inches of snow are highest (>50%) in
the Olympics, Cascades, and NorCal ranges (Shasta Siskiyous,
Trinity, Klamath, etc.) above 5000ft.


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


Fracasso