Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
334 AM EDT Sat Oct 21 2023

Valid 12Z Sat Oct 21 2023 - 12Z Tue Oct 24 2023

...Northern Rockies...
Day 3...

Split flow emerging across the western CONUS will result in a fast
northern jet streak arcing into the Pacific Northwest D3. On the
leading edge of this feature, the favorable left-exit region will
drive modest upper diffluence for ascent, aided by weak PVA as
vorticity streamers race through the pinched mid-level flow. At
the same time, a surface cold front will drop southward out of
Alberta/Saskatchewan, causing post-frontal upslope flow into the
terrain of the Northern Rockies late in the forecast period. As
snow levels collapse to around 2000 ft, this should result in
periods of accumulating snow driving moderate accumulations. WPC
probabilities for more than 4 inches of snow are confined to the
area around Glacier N.P., where they reach 20-30%, highest above
6000 ft.


Weiss