Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
653 PM EDT Wed Oct 7 2026

Valid 00Z Thu Oct 08 2026 - 00Z Sun Oct 11 2026

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

Positively-tilted troughing over the Gulf of Alaska amplifies as it
digs down the BC coast Thursday/Thursday night and further deepens
into a mid-level low over Washington Friday night. Strong lee-side
cyclogenesis downstream of trough/low occurs Friday into Saturday
with a strengthening low track over eastern Montana into North
Dakota.

Additional troughing extends from this low down the West Coast
Friday into Saturday, drawing tropical Pacific moisture north over
the Intermountain West. The surface low aids moisture draw up the
Plains and pushes a cold front over western Montana and the
Northwest Friday into Saturday bringing cool Canadian air south.

Snow breaks out over east faces of Montana Rockies on Saturday with
a 50% probability of exceeding 4" for the Lewis Range in Glacier
National Park by 00Z Sunday.

The upper troughing persists over the West Coast/Interior Northwest
along with surface ridging shifting down the Canadian Rockies
Sunday, helping spread snow south into Wyoming and lower elevations
of Montana with potential for significant early season
accumulations.

The probabilistic WSSI is rather suppressed for levels above minor
snow impacts due to rather high snow criteria in the MT Rockies.


The probability of significant Days 1-3 ice across the CONUS is
less than ten percent.


Jackson