Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
213 PM EST Sat Nov 11 2023

Valid 00Z Sun Nov 12 2023 - 00Z Wed Nov 15 2023

...Pacific Northwest into the Northern Rockies...
Days 1-2...

Active pattern will continue over the Pacific Northwest for the
next couple of days. Lead front today moving across the Divide
will maintain some onshore flow early D1 (starting 00Z Sun) with
an additional several inches of snow to the higher terrain of the
WA Cascades and around Glacier NP before diminishing Sunday
morning. WPC probabilities for at least 4 inches of additional
snowfall after 00Z Sunday are highest (>50%) over the northern WA
Cascades and around Glacier NP/Lewis Range.

The next system will move ashore coastal WA for D2, with snow
levels rising ahead of the front to above 4500ft into Monday
morning. Much of the forcing with this next system will head into
British Columbia which will favor a more southerly flow rather
than the more favorable westerly flow like its predecessor. Thus,
IVT values are forecast to be lower which supports only light to
moderate snow over the WA Cascades. Probabilities for at least 4
inches of snow are moderate (>40%) over the northern WA Cascades.

...Northern California...
Day 3...

An upper trough (lagging vort max within a broader trough) will
likely close off into an upper low by D3 around 130W, allowing
broad SW flow to eventually carry moisture into NorCal by late D3.
By 00Z/15, snow may accumulate a couple of inches in the highest
elevations as snow levels likely rise to around 7000ft. WPC
probabilities for at least 4 inches of snow are low (around 10%)
at this time.


Fracasso