Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
445 AM EDT Sun Mar 26 2023

Valid 12Z Sun Mar 26 2023 - 12Z Wed Mar 29 2023

...Northern & Central Rockies to the High Plains...
Days 1-2...

Closed low over the ID/WY border this morning will slowly move
eastward and weaken today, but will still act to enhance snowfall
over the central ID ranges eastward through south central Montana
and into the Absarokas and Bighorns. Stationary front will linger
just east of the Divide as well with temperatures well below
freezing. WPC probabilities for at least 4 inches of snow are high
(>70%) in the terrain above about 4000-5000ft. Into Day 2, a
separate vort max over northern NV will swing through CO as 700mb
FGEN lifts northward over the eastern CO Plains into southwestern
NE and far northwest KS as an inverted trough briefly stalls over
the area early Monday. This area may see several inches of snow
before high pressure moves in, with 4" probabilities around
40-60%.


...New England...
Day 1...

Weakening parent low over Quebec will carry its occlusion through
New England as it weakens this morning, allowing the triple
point/coastal low to take over in the Gulf of Maine. Progressive
flow will keep the system moving but still allow for several
inches over far northern Maine in the deepest cold air. WPC
probabilities for at least 4 inches of snow are >50% over much of
northern Aroostook County.


...Oregon/California...
Days 2-3...

Potent upper low just west of Haida Gwaii will continue southward
just west of 130W to a position west of OR/WA by Monday afternoon.
Concurrently, a system over the northeast Pacific will combine
from the southwest and the feature will deepen quite smartly as it
wraps up offshore late Monday into Tuesday. Plume of moisture will
surge ahead of the low pressure and cold front into NorCal D2-3 as
precipitable water values rise to between +1 to +2 sigma. Low snow
levels around 2000-3000ft will rise as milder air is drawn in
ahead of the cold front, to around 4000ft (north) to over 5000ft
across the central/southern Sierra. Heavy snow is likely for the
higher terrain with snowfall rates 1-2"/hr possible on Tuesday as
the moisture plumes sinks southeastward. WPC probabilities for at
least 12 inches of snow are high over the Klamath/Shasta Siskiyou
and northern/central Sierra Nevada. Additional snow is likely
beyond this forecast period into SoCal and the Great Basin.


Fracasso