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QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
130 AM EST Tue Feb 25 2025

Valid 12Z Tue Feb 25 2025 - 12Z Fri Feb 28 2025

...Pacific Northwest through the Northern Rockies...
Day 1...

Strong surface low pressure will be moving eastward near the Strait
of Juan de Fuca, pivoting onshore beneath a strong but filling
upper level shortwave trough. This upper feature will weaken
rapidly as it gets replaced by upper level ridging, resulting in
the surface low eroding as it moves across WA state. E/SE of this
stacked system, the ongoing atmospheric river (AR) will persist
another 12 hours as reflected by GEFS/ECENS IVT probabilities,
surging moisture into the Pacific Northwest and Northern Rockies
D1. The lingering precipitation D1 is expected to be lighter than
the heavy amounts that have fallen already, but still should
result in heavy snow in the WA Cascades and Northern Rockies,
including the Bitterroots and Lewis Range, especially above
3000-3500 ft. In these areas, WPC probabilities for 6+ inches of
snow are high (>90%), and pass level impacts will continue until
snow wanes at the end of D1.


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

A modest wave of low pressure will move northeast from the Great
Lakes across New England Thursday into Friday, with an accompanying
cold front trailing in its wake. The low will likely track across
central New England, with the accompanying WAA causing
precipitation to expand in the form of snow across northern New
England. Although the system will be fast moving, brief heavy snow
is likely in the higher terrain of the White Mountains of NH where
WPC probabilities reach 30-50% for 4+ inches of accumulations.
Later D3, as the cold front passes to the east, post-frontal
upslope flow will develop into the Adirondacks and northern Greens,
with modest lake enhancement occurring into the Tug Hill Plateau.
In these areas, WPC probabilities for 4+ inches reach 30-50% as
well, but generally later in the D3 period than what will occur
across the NH terrain.


Weiss

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