Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
246 PM EST Sat Nov 14 2026

Valid 00Z Sun Nov 15 2026 - 00Z Wed Nov 18 2026

...Northern Appalachians...
Day 1...

A potent shortwave trough rotating south along the western
periphery of a closed upper-low will generate PVA out ahead of the
trough over the Northeast tonight. Sufficient low-mid level
moisture and boundary layer temperatures will support additional
periods of snow above 1,000ft along the Southern Tier of NY and
into the Catskills, Adirondacks, Green, and White Mountains. Areas
southwest of Syracuse and north of Binghamton, which were hit hard
from the first heavy snowfall of the season a couple days ago,
could receive another coating-2" of snow through early Sunday
morning. Similar snowfall totals are expected in the higher
elevations of the Adirondacks, Green, and White mountains with
localized amounts up to 3" possible. After sunrise Sunday, a
warming boundary layer and rising heights aloft will cause
accumulating snowfall to come to an end by midday.


...Western United States...
Days 1-3...

An active storm track, courtesy of a strong Pacific jet stream,
will direct yet another storm system at the West Coast tomorrow. An
atmospheric river (AR) associated with a potent northeast Pacific
cyclone will reach the West Coast this evening with CAA in wake of
the storm's cold frontal passage causing snow levels to lower over
the Cascades, Olympics, and Siskiyou/Shasta mountains by Sunday
morning. The air-mass is not especially cold, considering the
source region is from the North Pacific, so snow levels in the
Cascades, Olympics, and southward to the Siskiyou/Shasta/Salmon
mountains of northern CA are generally expected to hover around
4,000ft at the lowest through the start of the week. Probabilities
for snowfall totals >4" are >50% for elevations above 5,000ft. Of
the notable passes potentially affected, Washington Pass shows low
chances (10-30%) for snowfall totals exceeding 4" through early
week.

The footprint of the AR will stretch southward into the Sierra
Nevada with the heaviest snowfall expected Sunday night and into
the day on Monday. Snow levels as low as 5,000ft are possible in
the northern Sierra Nevada, but areas of heavier snowfall are
likely to reside at/above 6,000ft in elevation. Latest
probabilities show moderate chances (40-60%) for snowfall totals
>6" along I-80 near Donner Pass and low-to-moderate chances
(20-40%) along US-50 near Phillips and Twin Bridges. WSSI-P shows
greater confidence in Minor Impacts (winter conditions; use caution
while driving) at these aforementioned CA passes (50-70% odds), but
it is noteworthy that there are low chances (10-30%) for Moderate
Impacts which suggest the potential for travel disruptions.

The AR works its way farther inland across the Great Basin and
northward across the Blue Mountains and Northern Rockies beginning
Sunday night. The upper trough slows down as it moves into the
Intermountain West late Monday and into Tuesday, providing a
prolonged window for light-to-moderate snowfall rates across the
mountain ranges through the first half of the week. The mountains
ranges seeing the longest period of favorable upper-level
divergence, anomalous moisture aloft, and upslope enhancement are
the Blue and Sawtooth Mountains. Latest probabilities depict high
chances (>70%) for >8" of snow in the Blue Mountains and moderate
chances (40-60%) for snow totals >12" at/above 6,000ft. By Monday
night, PWs across the Northern Rockies approach the 97.5
climatological percentile, providing more than enough moisture to
support accumulating mountain snow. The AR will have cleared the
Sierra Nevada by Tuesday morning and mountain snow will work its
way east across the Great Basin and towards both the Wasatch and
Uinta. Latest probabilities show high chances (>70%) for >6" of
snow in the southern reaches of the Wasatch and the more remote
elevations of the Bitterroots. Some minor snowfall amounts
(generally less than 2") in the valleys of western MT at elevations
as low as 3,000ft, but most heavy snowfall amounts will reside
above 7,000ft in the Bitterroots late Monday into Tuesday.


The probability of significant ice across the CONUS is less than
10 percent.


Mullinax