Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
401 PM EST Sun Dec 22 2019

Valid 00Z Mon Dec 23 2019 - 00Z Thu Dec 26 2019


Days 1-3...

...Southwestern U.S....

A series of shortwaves moving through the base of a longwave
trough will produce periods of organized snow with locally heavy
accumulations from the mountains of central to southern California
to the ranges of southern to central NV, southern UT, northern AZ,
and southwest CO through mid week.

A slow-moving frontal boundary drifting east across California
tonight through Monday allows the band of lift and moisture to
drift slowly across the southern Ca Sierra Nevada mountains, with
a coupled upper jet pattern producing 300 mb divergence maxima
that result in several inches of snow. A low level wave develops
along the front and approaches the Southern California coast
Monday, bringing locally heavy snowfall accumulations for the
Transverse Ranges.

The 700 mb wave drifts east across NV/southern CA on Tue, with the
pre-frontal moisture and upper level jet and lift progressing into
the ranges of central to northern AZ and then southern UT,
eventually reaching southwest CO.

The wave departs UT across CO/NM on Wed., with the longer duration
snows and resulting higher amounts in the ranges of CO.  The snow
coverage and intensity winds down as the 700 mb wave departs onto
the Plains.  The heaviest 2 day totals are expected in the San
Juan Mountains in Colorado, with several additional inches
expected.

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

Petersen