Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
337 AM EST Fri Nov 27 2020

Valid 12Z Fri Nov 27 2020 - 12Z Mon Nov 30 2020

Days 1 to 3...

...Southwest U.S...
 
For Friday and early Saturday, the latest models are in very good
agreement in developing an upper low over Arizona that moves east
across New Mexico and then out into the southern High Plains by
Saturday night. The system overall will be rather
moisture-starved, but lift from the combined upper divergence/low
level convergence maxima near the low center and areas of upslope
flow is expected to yield a few pockets of 3-5 inches of snow over
the higher terrain of the mountains of central New Mexico and
adjacent east central Arizona. Amounts taper on the high Plains
with low QPF and mixed precip types and duration.

...Pacific Northwest...

A shortwave trough will brush the Pacific Northwest Friday night
and early Saturday and drive a weak cold front across the WA
Cascades. Sufficient onshore flow is expected to combine with
ascent focused as a jet maxima crosses Fri night to Sat morning,
supporting upper divergence maxima across the region. The
combination of jet-induced lift and orographics should result in
several inches of snow in the northern WA Cascades Friday night to
early Saturday.

For Days 1-3, the probability of significant icing (0.25 inch or
greater) is less than 10 percent.

Petersen