648
FOUS11 KWBC 122011
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
311 PM EST Wed Nov 12 2025

Valid 00Z Thu Nov 13 2025 - 00Z Sun Nov 16 2025


...California...
Days 1-3...

A strong 750+ kg/m/s atmospheric river (AR) will begin to make
landfall across far northern California late tonight before
gradually working its way down the length of the state through
Saturday. This potent but transient AR will transport copious
amounts of moisture (PW anomalies in excess of 250-300% of
normal), leading to heavy mountain snows across the Sierras the
next few days (particularly Day 2). Recent model trends advertising
the slower inland progression of a cut-off upper low off the coast
of California continue today, leading to higher snow levels above
8-10kft within an extended WAA regime through the period.

The latest WPC 72-hr snow probabilities >12" across the Sierras
(above 8kft) are high (70-95%) while probabilities >24" are
moderate (40-70%).


...Pacific Northwest through the Northern Rockies...
Days 2-3...

North of the cut-off low off the coast of California, a sheared off
shortwave will reach the Pacific Northwest coast late Thursday and
work its way east across the northern Rockies through Friday. High
snow levels above 8-9kft in the warm air advection ahead of the
trough generally drop to around 5kft late Thursday into
Friday. Given the separation between the northern shortwave and the
cut-off low/atmospheric river well to the south, available moisture
will be fairly limited across the Pacific Northwest. This should
keep snowfall rates across the high terrain low to moderate.

The latest Day 2-3 WPC 48-hr snow probabilities >8" across the
Washington Cascades and northern Rockies are moderate (40-80%).


...Interior Northeast...
Days 1-2...

Persistent troughing continues over the Northeast the next few
days as a series of impulses move through the northwesterly flow
aloft. These impulses combined with a renewed cold advection regime
blowing across the warm eastern Great Lakes will result in bands
of lake enhanced precipitation. This will likely lead to some
additional snowfall downstream of Lake Ontario east of the Finger
Lakes into the Catskills. Cold upslope flow will also lead to
persistent snowfall across portions of the northern Adirondacks,
Greens, and higher Whites of New Hampshire. Only light snow is
forecast on Northeast terrain in the flow wrapping around a
developing low north of Maine later Friday into Saturday.

The latest Day 1 WPC 24-hr snow probabilities for >4" are moderate
(30-70%) across portions of the Tug Hill, Adirondacks, and east of
the Finger Lakes into the Catskills. Meanwhile, Day 1-2 48-hr snow
probabilities for >12" are moderate (40-80%) across the Greens,
and higher Whites, with 20-40% probabilities for >18".


The probability of significant icing is less than 10 percent.


Miller






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