Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
339 AM EST Sun Dec 23 2018

Valid 12Z Sun Dec 23 2018 - 12Z Wed Dec 26 2018


...Western U.S....

Mid-level energy embedded within progressive onshore flow will
promote periods of snow across the Olympics, Cascades and portions
of the northern Rockies, producing additional heavy accumulations
through Sunday.

Focus for heavy snow will begin to shift further south on Monday,
as a well-defined shortwave moving dives southeastward into
northern California Monday night.  This is expected to bring
locally heavy accumulations from the southern Cascades into the
northern Sierra, with significant acucmulations also possible
further to the east into the higher elevations of the Great Basin.

As the shortwave continues to dig southeast, with an upper upper
low closing off over Southern California and the Southwest, snows
will shift further south and east, reaching into eastern Arizona
and western New Mexico and western Colorado late Tuesday into
Wednesday.

The probability of signficant icing (0.25 inch or more) is less
than 10 percent. 

Pereira