Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
605 PM EDT Thu Sep 29 2022

Valid 00Z Fri Sep 30 2022 - 00Z Mon Oct 03 2022

...North-Central Rockies...

Days 1-3...

An upper low will amplify and drop southeast from the Pacific
Northwest into the Central Rockies through the weekend. This will
result in downstream mid-level divergence to provide ascent, aided
by modest upper diffluence Friday into Saturday and some upslope
enhancement on W/SW 700mb moist flow. This upper low will then
pivot nearly in place Saturday as flow becomes blocked to the east
by a mid-level ridge, with subsequent filling occurring into
Sunday /D3/. While the best ascent appears to occur D1, steep
lapse rates beneath the core of the upper low combined with
continued upslope flow and lowering snow levels will still provide
an environment supportive of moderate to heavy snow. Snow levels
through the event will drop to around 9000 ft, and as moisture
surges northward from both the Gulf of Mexico and the Pacific/Gulf
of California. Despite modest SLRs, the increase in QPF has led to
an uptick in snowfall, with local amounts above 12 inches possible
during the 3 days, especially in the highest terrain of the
Absarokas and Wind Rivers.


For days 1-3, no icing is forecast.

Weiss