Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
244 AM EDT Sat Apr 12 2025

Valid 12Z Sat Apr 12 2025 - 12Z Tue Apr 15 2025


...Northern Mid-Atlantic to New England...
Day 1...

Storm system just off the DelMarVa this morning will continue to
lift northeastward to a position just east of Cape Cod by early
Sunday morning. With an amplified jet, moisture already across much
of the northern Mid-Atlantic into the Northeast will turn to snow
as temperatures cool just enough on northeasterly surface flow.
Snow will pick up in intensity toward daybreak, and by the start of
this period (12Z Sat), moderate snow is likely (rates >1"/hr) over
parts of the Catskills, Berkshires, and Green and White Mountains
through mid-day. By this afternoon, drier air toward the mid-levels
will help decrease any snow or rain/snow mix across much of the
area except for northern New England where temperatures will rise
to around freezing where snow continues to fall. Precipitation will
mostly end by early Sunday but continue over northern Maine into
the afternoon. WPC probabilities for at least 4 inches of snow are
highest (>50%) over the higher elevations above 1000-1500ft or so
with 1-3" over lower elevations and a rain/snow mix with little
accumulation in the lowest elevations (valleys and near the water
south of I-90).


...Northern to Central Rockies...
Days 1-2...

A strong mid-level shortwave over WA this morning will strengthen
across ID/MT today, promoting light to modest WAA-driven snow over
NW MT/northern ID into northern WY as the upper jet slips
southeastward into the Plains. Temperatures will fall behind the
front and lower snow levels to below 4000ft as precipitation
lightens and then ends from west to east on Sunday/Sunday night. By
then, the cold front will slow across the central Rockies, helping
to wring out some snow over CO. The system will be fairly
progressive overall but it could snow moderately (>1"/hr) for a
time this evening over NW MT and NW WY. WPC probabilities for at
least 6 inches of snow for the period are highest around Glacier
NP, across the Little Belt Mountains, and near Yellowstone NP
(30-60% probs). Over the CO Rockies, amounts will be lighter
overall, but some areas could still see several inches of snow
(above 10,000ft). There, WPC probabilities for at least 6 inches of
snow are 40-60%.


...Western Great Lakes...
Day 3...

The mid-level low exiting MT Sunday will strengthen more over the
northern Plains as a 120kt jet streak develops over Iowa. An area
of surface low pressure will deepen and help foster an expanding
area of precipitation over the northern Plains into the Upper
Midwest. Temperatures will be marginal to mild initially, but once
the low tracks into Lake Superior, north to northwest winds will
bring in colder air to northern areas of MN and eventually into the
U.P. of Michigan Monday night into early Tuesday. Snow will become
more widespread with accumulation likely over most of the MN
Arrowhead and northern WI into the U.P. of Michigan. There, WPC
probabilities for at least 4 inches of snow through 12Z Tue are
moderate (40-70%).


The probability of at least 0.10" of freezing rain across CONUS is
less than 10%.


Fracasso