Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
256 AM EST Thu Nov 13 2025

Valid 12Z Thu Nov 13 2025 - 12Z Sun Nov 16 2025


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

A strong 750+ kg/m/s atmospheric river (AR) will continue to push
inland across far northern California this morning before
gradually working its way down the length of the state through
Saturday, while also weakening somewhat. This potent but transient
AR will transport copious amounts of moisture (PW anomalies above
the 99.5th percentile per the 12z NAEFS), leading to heavy
mountain snows across the Sierras primarily above 8kft the next
few days. After this AR impacts the Sierra today and Friday, an
associated upper low is expected to become cutoff from the westerly
flow to the north and linger off the southern California coast on
Saturday before swinging inland Saturday night. This is likely to
lead to another burst of heavy mountain snow across the
central/southern Sierra by the end of Day 3. Uncertainty regarding
the timing of this upper low remains a forecasting challenge, with
a trend towards slower inland progression becoming most likely.
This has also led to recent model trends advertising higher snow
levels above 8-10kft within an extended WAA regime through the
period.

The latest WPC 24-hr snow probabilities >12" across the Sierra are
highest on day 1 and again across the southern Sierra on day 3 with
values between 60-80% for each day. Snowfall totals >24" are
possible above 10kft, with WPC probabilities around 60-90% for
72-hr storm total amounts.


...Interior Northeast...
Days 1 & 3...

Persistent troughing continues over the Northeast the next few
days as a series of impulses move through the northwesterly flow
aloft, with a separate and stronger shortwave moving into the
region by Day 3. These impulses combined with a renewed cold
advection regime blowing across the warm eastern Great Lakes will
result in bands of lake enhanced precipitation through Friday.
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.

The latest Day 1 WPC 24-hr snow probabilities for >4" are moderate
(30-70%) east of the Finger Lakes into the Catskills. Meanwhile,
Day 1 snow probabilities for >8" are moderate (40-80%) across the
Greens and higher Whites.

By Day 3, a WAA regime with lingering low-level cold air will allow
for a brief period of freezing rain across the northern Adirondacks
and northern New England. WPC and NBM probabilities for >0.1" of
ice are between 10-30% for this region on Day 3, with additional
wintry precipitation likely on Day 4.


Snell