Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
314 AM EST Wed Dec 20 2023

Valid 12Z Wed Dec 20 2023 - 12Z Sat Dec 23 2023

...Sierra Nevada to the Southwest...
Days 1-3...
An upper low centered off of the coast of Northern California will
continue to drop south today, shifting the better moisture
advection and potential for heavy snow farther south into the
southern Sierra Nevada.  WPC PWPF shows a small area of moderate
to high probabilities for additional accumulations of 8 inches or
more through early Friday centered around the Sequoia and Kings
Canyon National Park areas for elevations above 8000 ft.

By early Friday, models show the low beginning to swing inland
along the U.S.-Mexico border into the interior Southwest Friday
night.  Snow levels are expected to be at or above 8000 ft across
much of the Southwest Friday morning, before dipping to around
7000 ft as the upper low moves across the region.  Deep
southwesterly flow and upper forcing centered ahead of the
approaching the low will support heavier precipitation across
southern Arizona, including the White Mountains, where WPC PWPF
indicates that heavy snow accumulations are likely across the
higher terrain.

...Pacific Northwest to the Northern Rockies...
Day 3...
A northern stream shortwave will advance steadily across the
northeastern Pacific, reaching the Pacific Northwest on Friday. 
Light to moderate precipitation will spread across the Northwest
into the Rockies as snow levels drop below 2000 ft across much of
the region by early Saturday.  While widespread heavy
accumulations are not anticipated, at least a few inches of snow
can be expected along the Cascade passes Friday into early
Saturday.

Pereira