FOUS11 KWBC 202018

QPFHSD



Probabilistic Heavy Snow and Icing Discussion

NWS Weather Prediction Center College Park MD

418 PM EDT Fri Mar 20 2026



Valid 00Z Sat Mar 21 2026 - 00Z Tue Mar 24 2026



...Northeast... 

Days 1-3...



A clipper will move into the Northeast Saturday night bringing a 

swath of accumulating snowfall to Upstate NY into Northern New 

England. Still some uncertainty with the exact track of this 

system, which will impact where the heaviest swath of QPF is and 

where the rain/snow line sets up. The higher elevations are most 

favored for higher snowfall totals, but strong WAA should support a

period of moderate to locally heavy precipitation. This should 

allow snow even down to the lower elevations of northern New 

England, especially Saturday night into early Sunday. Snow ratios 

from the NBM are likely too high with this system. While snow 

should be coming down at a decent clip for a stretch, the strongest

lift appears to be mainly centered below the DGZ, which should cap

snowfall ratios. Then during the daylight hours the late March sun

will play a role in lowering ratios further. In fact, where snow 

is falling at a lighter clip we probably won't see much 

accumulation during the daytime, with accumulations focused in 

either the highest terrain or where snow is falling at a heavy 

enough clip to overcome the marginal temperatures and higher sun 

angle.



The latest WPC snowfall probabilities have increased for the

Saturday night to Sunday timeframe. The probability of exceeding 4"

in the 24hr period ending 00z Monday are generally 40-80% from 

Upstate NY into central to northern VT/NH and western ME. The 

highest probabilities are in the higher terrain, but values of 

30-50% even get into the lower elevation areas. The probabilities 

of 6" are 30-60%, with 8" exceedance probabilities as high as 

30-50% in the White Mountains of NH. These probabilities seem 

reasonable, with exact snowfall totals dependent on the specific track

of the system. This is a scenario where the higher terrain has the

highest probabilities (and thus confidence) in seeing greater 

snowfall totals, but there is still a lower risk of impactful snow

getting into some of the lower elevations if a snowfall band is 

able to move into these areas overnight or early morning and is 

heavy enough to overcome the marginal temperatures.



A bit more uncertainty exists on Monday as a coastal low tries to

develop offshore New England. By this time it will be cold enough

over northern New England for snow, but if precipitation intensity

is light then the high sun angle will likely limit accumulation.

However, a broader and/or more intense snow shield would be 

capable of producing additional accumulating snowfall. Models have 

been fluctuating regarding this low and inland precipitation 

extent...although most 12z models shifted lighter with QPF. Even 

the AIFS, which has been more consistently on the wetter side of 

the QPF spectrum, did back off at 12z. There is still time for this

to change, but the probabilities of impactful snowfall Monday 

appear to be decreasing, but still need to continue to monitor.



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

percent. 





Chenard





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