Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
310 AM EDT Sun Apr 13 2025

Valid 12Z Sun Apr 13 2025 - 12Z Wed Apr 16 2025


...Maine...
Day 1...

Upper trough will finally start to push east of 70W today with the
last wave lifting toward the Gulf of Maine. Rain along the coast
and snow inland will slowly ease out of the area overnight tonight
into early Monday, with some modest QPF amounts that have trended
up in just the past 24 hrs (with a slower exit of the system
altogether). Temperatures remain marginal for most areas, but snow
should still accumulate over northwestern Maine and in the higher
elevations even during the daytime when precip rates may be
highest. Still, SLRs will be not much better than about 7-9:1,
making for a west and heavy snowfall. WPC probabilities for at
least 4 inches of snow after 12Z today are at least 40% over much
of northern Maine, with low probabilities (10-30%) of at least 8
inches in some of the highest elevations.


...Northern to Central Rockies...
Day 1...

A strong/compact upper low will move out of western MT this
morning, with some with some trailing snow along a surface trough
axis back toward the middle of the state that will end late this
afternoon. To the south, a weaker shortwave will move from UT to
CO, helping to wring out some snow for the high Rockies and lighter
snow below 7500ft as colder air comes in. WPC probabilities for at
least 4 inches of snow after 12Z today are moderate (40-70%)
across some of the central MT mountains (e.g., the Little Belts)
and over the northern CO Rockies (above 10,000ft).


...Western Great Lakes...
Days 1-2...

The mid-level low exiting MT today will strengthen more over the
northern Plains as a 120kt jet streak develops over Iowa. An area
of surface low pressure at the tip of this jet will deepen over
northern WI and help foster an expanding area of precipitation
throughout the region. Temperatures will be mild initially (upper
50s into central MN/WI), but once the low tracks into Lake
Superior, north to northwest winds will rapidly bring in colder air
to northern areas of MN and eventually into the U.P. of Michigan
Monday night into early Tuesday. Rain will change to snow and
become more widespread with accumulation likely over most of the MN
Arrowhead and northern WI into the U.P. and northern Lower
Michigan. By Tuesday, with the surface low well into Ontario,
northerly winds will advect in 850mb temperatures of around below
-6C which may be enough to spur some lake enhancement (Lake
 Superior temperatures around 4-5C). The snow will end from west to
 east on Tuesday. WPC probabilities for at least 4 inches of snow
 through 00Z Wed are moderate (30-60%) in northeastern MN. For
 areas downwind of Lake Superior (far northern WI through the U.P.
 of Michigan), higher amounts are likely Monday night through
 Tuesday, with WPC probabilities depicting 20-60% chances for at
 least 8 inches of snow in the favored areas just inland from the
 lake shore and with any elevation (e.g., Porcupine and Huron
 Mountains). For northern Lower MI, WPC probabilities for at least
 4 inches of snow are low (10-30%).


...The Northeast...
Day 3...

Low pressure will continue through Canada with its cold front
rushing across the Northeast on Tuesday. Behind it, colder air will
filter in with lingering precipitation downwind of the eastern
Great Lakes with some upslope in the central Appalachians as well.
Temperatures will be marginal for some lower elevations and also
near the lake waters, but light accumulation is likely over much of
western and northern NY (Chautauqua Ridge, Tug Hill Plateau,
Adirondacks). There, WPC probabilities for at least 4 inches of
snow are 10-60%, highest in the Adirondacks.


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


Fracasso