763
FOUS11 KWBC 210718
QPFHSD

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

Valid 12Z Fri Nov 21 2025 - 12Z Mon Nov 24 2025


...California & Southern Rockies...
Days 1-3...

A Pacific upper low near the central CA coast this morning will
continue to drop south-southeastward today into a position just
west of the northern Baja Peninsula by early Saturday. A
combination of healthy PVA, upslope flow, and a modest moisture
feed will promote periods of snow for the southern Sierra and SoCal
ranges today (San Rafael/San Gabriel/San Bernadino/San Jacinto).
Snow levels will continue to tick downward to between 5500-6000ft.
With the upper low so far south of the region by tomorrow, the
colder temperatures aloft will be displaced southward and
diminished upslope flow will reduce precipitation rates. Snow
levels will rise and change snow to rain below 7000ft before ending
midday Saturday. The upper low will begin to push eastward
Saturday night through Sunday and spread moisture across AZ into NM
and CO with snow at high elevations (generally above 8000-9000ft).
The upper low will pick up speed Sunday evening and lift through
CO and weaken into an open wave over the High Plains by early
Monday. Along and near its path, modest snow is expected over the
San Juans and Sangre de Cristos but snow levels will remain high
through the event (no lower than about 7500ft which will be at the
end of the event).

WPC probabilities for an additional 6 inches of snow today are
>50% above about 10,000ft over the southern Sierra. Across the
SoCal Mountains, with a longer duration of precipitation today, a
significant heavy/wet snowfall is likely to continue. WPC
probabilities for an additional 6 inches of snow are >50% above
8000ft. This could cause locally significant travel disruptions
over these higher elevations, along with the potential for some
tree damage and infrastructure impacts given the heavy/wet
consistency of the snowfall. The WSSI does depict some Moderate to
locally Major Impacts in the San Gabriel and San Bernadino
Mountains above 8,000ft.

In the Southern Rockies, 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.

...Pacific Northwest...
Day 3...

Quasi-zonal flow out of the Northern Pacific will bring in a
rather strong frontal system to WA/OR/ID and northwestern MT
Sunday. Snow levels around 5000-6000ft Sunday afternoon will drop
to below 3000ft by early Monday as precipitation lightens. Some
significant snow may impact the higher passes where WPC
probabilities for at least 6 inches of snow are >50% above about
4000-4500ft. Snow will also spread across northern ID into
northwestern MT late Sunday/early Monday with snow continuing
beyond this forecast period.

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

A clipper system associated with a shortwave and dip in the jet
stream will push quickly through southern Ontario/Quebec and
northern NY/New England Sunday afternoon/evening. QPF amounts
appear light, and generally only an inch of two of snow is
expected. WPC probabilities for at least 4 inches of snow are less
than 10 percent, though the NBMexp (v5.0) probabilities max out
between 15-25% over the northern Green Mountains of VT.


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

Fracasso


$$