Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
343 PM EST Mon Dec 23 2019

Valid 00Z Tue Dec 24 2019 - 00Z Fri Dec 27 2019


...California to the Rockies...
Days 1-3...

An amplified trough off southern CA will greatly weaken as it
ejects northeast to the central Rockies through Tuesday night.
Pacific moisture of tropical origin will continue to shift in
ahead of the trough axis and result in periods of moderate to
locally heavy mountain snows across the Four Corners states
through this time. WPC probabilities for 12 inches are low to
moderate for the highest terrain of AZ/southern UT/southern NV on
Day 1, shifting to western CO for Day 2.

A second system in the mean trough digs south off the West Coast
through midweek before developing into a closed low off southern
CA Wednesday night. Heavy precipitation will be focused on
southern CA with snow levels around 4000ft. Day 3 WPC
probabilities for 12 inches or more of snow are generally moderate
for the southern Sierra and high over the highest Transverse
Ranges. There is a risk for two to three feet of snow on the
highest Transverse Ranges in the Day 3 time frame.

...Northern Minnesota...
Day 3...

The remnants of the low ejecting northeast from off southern CA
tonight reforms Wednesday as it interacts with northern stream
energy over the northern Plains. As this low tracks north across
the upper MS Valley there is a risk for moderate snow over
northern MN. Day 3 WPC probabilities are rather low for 4 inches
or more, but moderate over the far northwest and the Arrowhead.

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

Jackson