Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
331 PM EDT Wed Oct 13 2021

Valid 00Z Thu Oct 14 2021 - 00Z Sun Oct 17 2021

...Colorado...
Days 1/2...

A reinforcing shortwave trough brings an upper trough axis across
the Central Rockies through Thursday. Westerly flow will provide
upslope enhancement over the central Colorado ranges where WPC
probabilities of at least 4 inches of snow from 12Z Thursday
through 12Z Friday are 40 to 80 percent, generally above 7,000 ft.
Furthermore, lee-side troughing will allow some easterly flow to
enhance snow potential over the Palmer Divide where snow
probabilities for 4 or more inches have lowered to around 10%.


...Western Washington...
Day 3...
An Atmospheric River sends a surge of moisture across western
Washington Friday night and Saturday. Precipitable water values of
1.25 inches, about 2 standard deviations above normal, are
expected to push inland across the Olympic Peninsula to the
Northern Cascades. However, in this warm airmass, snow levels will
be above 8,000 ft, restricting snowfall to the highest elevations
of the Northern WA Cascades.


The probability for significant icing (0.25 inches or more) is
less than 10 percent Days 1-3.

Jackson/Zavadoff