Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
345 PM EDT Wed Nov 02 2022

Valid 00Z Thu Nov 03 2022 - 00Z Sun Nov 06 2022


...Four Corners and Central Rockies...
Days 1-2...
Digging troughing currently over the Pacific Northwest will
continue to deepen as it approaches the Southwest U.S. and Four
Corners region over the next 24-36 hours. The combination of
strong height falls and forcing for ascent will favor heavy
snowfall initially across the Sierra followed by the Unitas and
southern UT and northern AZ ranges. As the system closes off later
in the day 1 period, the strong lift coupled with orographic
enhancement will bring higher totals to the CO Rockies and San
Juans of southern CO and northern NM where totals are expected to
exceed a foot (localized 18-24" 2-day totals possible). Outside of
the CO Rockies, as colder air seeps down, a narrow corridor of
snow is possible Thursday afternoon/evening and could bring a few
inches of accumulation east of the mountains. To the north, the
Wyoming ranges will likely pick up appreciable accumulations due
to convergence and upslope/terrain enhancements, especially the
Wind River Range and Bighorn Mountains.

The latest WPC snow probabilities for 4" or more are high for the
terrain areas of UT, western/central CO, WY, and northern AZ. The
greatest probabilities for exceeding 12" are for the San Juans of
southern CO, the Unitas in UT, and the southern UT ranges.


...Western U.S....
Days 2-3...
After a brief break between storm systems, the next atmospheric
river begins to approach the Pacific Northwest late Thursday
through Saturday. Forecast guidance is consistent on showing the
approach of a 150+ kt jet from British Columbia sagging southward
into Oregon during the period with a plume of higher moisture
nosed directly on western WA and OR. Initially, snow levels will
be low enough for heavy snow across the higher peaks of the WA
Cascades, but as warm air takes over, the snow will be confined
mainly to the highest peaks. Before that happens, accumulations of
8-12"+ are likely with localized higher amounts exceeding a foot.
Farther east, snow levels will be a bit lower over
northern/central ID into western MT where modest snowfall is
likely. WPC probabilities for at least 4 inches of snow are high
(above 4000 ft) and the higher elevations have high probabilities
for at least 8 inches of snow.

The probability of significant icing greater than 0.25" is less
than 10 percent.

Taylor