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FOUS11 KWBC 211920
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
220 PM EST Fri Nov 21 2025

Valid 00Z Sat Nov 22 2025 - 00Z Tue Nov 25 2025


...Southern Rockies...
Days 2-3...

The upper-low that produced heavy mountain snow in the peaks of the
southern California mountains will make its way through northern
Mexico Saturday night. Healthy subtropical moisture will be
directed at the Southern Rockies at the same time as diffluent flow
aloft supports upper-level ascent atop the atmosphere. Add in the
favorable upslope component into mountain ranges such as the Gila
Mountains, the San Juans, and the Sangre De Cristo, and this
upper-low will produce snow in the Southern Rockies. Snow begins in
the AZ/NM mountains Saturday evening, then begins in far northern
NM and the CO Rockies on Sunday. Some lingering snow showers may
persist in the remote peaks of the Southern Rockies through early
Monday morning before concluding Monday afternoon.

Given the lack of a cold antecedent air-mass, snow levels will
struggle to dip much lower than 7,000ft. In terms of where the
heaviest snowfall is most likely to occur, elevations above 9,000ft
in the Mogollon Rim and Gila Mountains are most likely, while
heavy snow will be mostly confined to the more remote elevations
above 10,000ft in the San Juans and Sangre De Cristo. WPC
probabilities for at least 8 inches of snow primarily on Day 3
(Sunday) are >50% above about 11,000ft in the more remote/higher
ridge lines of the San Juans and especially the Sangre De Cristo
range. WPC probabilities show low-to-moderate chances (20-50%) for
storm total snowfall >8" for all the mountains and elevations
referenced, although the higher end of those probabilities applies
mostly to the highest and most remote sections of the Southern
Rockies.

...Pacific Northwest & Northern Rockies...
Days 2-3...

A Pacific disturbance embedded within uasi-zonal flow will usher in
a progressive, but potent, frontal system into WA/OR/ID and
northwestern MT Sunday. As the cold front traverses the Pacific
Northwest, snow levels around 5000-6000ft Sunday afternoon will
drop to as low as 2,000ft on the windward side of the Cascades by
early Monday as precipitation begins to taper off. WPC
probabilities for >4" of snow do range between 30-50% in both
Stevens and Snoqualmie Passes, with potentially upwards of 6"
possible. Snow will also spread across northern ID into
northwestern MT late Sunday and through Monday as moisture
associated with the Pacific system moves through. Additional heavy
snowfall may ensue along the Lewis Range on Monday as strengthening
high pressure to the north gives rise to strengthening easterly
upslope flow. WPC probabilities show moderate-to-high chances
(50-80%) for snowfall totals >8" in the Lewis Range through Monday
afternoon. The highest elevations of the Lewis Range may top 12"
in spots through Monday afternoon.

...Northeast...
Days 2-3...

A clipper system rotating beneath the base of an broad upper-low
over Quebec will push quickly through northern NY/New England
Sunday evening and exit the to the east by Monday morning. Guidance
shows some uncertainty on the strength of the approaching clipper
system with the GFS/CMC showing a more amplified solution while the
ECMWF/UKMET camp is less amplified and features less QPF. Even
taking the average of these solutions, it would lead to some minor
snowfall accumulations (1-4") across the Tug Hill, the
Adirondacks, and both the Green and White Mountains. At this
moment, WPC probabilities show low-to-moderate chances (20-50%) for
snowfall totals >4" in these ranges with elevations above 2,000ft
most favored for accumulating snowfall.


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

Mullinax





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