FOUS11 KWBC 200701

QPFHSD



Probabilistic Heavy Snow and Icing Discussion

NWS Weather Prediction Center College Park MD

301 AM EDT Fri Mar 20 2026



Valid 12Z Fri Mar 20 2026 - 12Z Mon Mar 23 2026



...Upper Great Lakes to the Northeast... 

Days 1-3...



The first in a series of clipper systems will produce periods of

snow across northern New York and northern New England today. Low-

level WAA ahead of the clipper will support periods of snow, even

down to the valley floors in northern New England. However,

snowfall rates and elevation will play critical roles in snowfall

accumulations. Most notably, the Adirondacks, Green, and White 

Mountains are most favored for >1"/hr snowfall rates. WPC 

probabilities depict localized moderate probabilities (40-60%) for 

snowfall totals >4" with the peaks of these mountain ranges 

(including Mt. Washington) sporting low chances (10-30%) for 

snowfall accumulations as high as 6". Otherwise, most elevations 

below 1,000ft are likely to see anywhere from a coating to as much 

as 3". The WSSI does depict some Minor Impact potential, 

particularly in the Adirondacks and bordering the St. Lawrence 

River in NY's North Country. Snow will taper off across northern 

New England by Friday night.



As this clipper exits to the east Saturday morning, the next 

clipper system is already making its way towards the Upper Great

Lakes. There remains a decent amount of model spread in the

amplitude and progression of this clipper, largely because it is

essentially an unorganized cluster of sheared 500mb vort maxima

tracking over the northern Great Lakes and Northeast. There will be

sufficient upper-level ascent thanks to the left-exit region of a

500mb jet streak will accompany the clipper. There is also

agreement on model guidance on healthy 850-700mb WAA via WSWrly

flow that collides with sufficiently cold boundary layer

temperatures over northern NY and the rest of northern New 

England. However, guidance is not yet in agreement on where the 

strongest 850-700mb FGEN takes shape, and as a result, disagree on

the placement of the QPF axis to the north of the storm track. WPC

Day 3 cluster analysis shows the departing trough over Nova Scotia

and the depth of the primary 500mb shortwave trough over the Upper

Midwest are the most sensitive factors in determining what this 

clipper ultimately produces, and because of the notably shorter 

wavelengths, confidence in where the heaviest snowfall will occur 

is not clear out to Day 3. 



So what we do know-- It is late March and elevation matters a ton.

However you slice it across deterministic guidance or 

probabilistic guidance, the Adirondacks, Green, Whites, and 

Berkshires are most favored for accumulating snowfall. Even as far 

west as the MI U.P. and MN Arrowhead, snowfall totals approaching 

4" are possible. WPC probabilities show low-to-moderate chances 

(30-50%) for snowfall totals >4" in the Hurons of the MI U.P. 

between Saturday night and through Sunday. Farther east, the 

>2,000ft elevations in the Adirondacks, Greens, and Whites sport 

moderate chances (40-60%) for snowfall totals >8" on Sunday. Below

1,000ft, probabilities for snowfall amounts >4" are low (10-30%) 

with most accumulations less than 4" expected at this time. WPC's 

WSSI-P depicts moderate chances (40-60%) for Minor Impacts in the 

MN Arrowhead to much of northern MI due to a combination of snow 

and ice (WPC probabilities show low-to-moderate chances, or 30-50%,

for ice accumulations of at least one-hundreth of an inch) late 

Saturday into early Sunday. Minor probabilities are highest in 

northern New England where moderate probabilities (40-60%) are 

present throughout the northern Appalachians. In fact, some

localized 40-50% probabilities for Moderate Impacts are shown

across south-central and Downeast Maine. 





The chances for significant icing across the CONUS is less than 10

percent. 





Mullinax









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