Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
223 AM EDT Thu Oct 8 2026

Valid 12Z Thu Oct 08 2026 - 12Z Sun Oct 11 2026

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

Troughing over the Gulf of Alaska this morning will push
southeastward into British Columbia Friday and elongate from
southwest to northeast on Saturday as it slowly digs southward.
This will spur lee-side cyclogenesis east of the Canadian Rockies
with low pressure deepening over eastern Montana to the High
Plains. With the trough axis down the West Coast, a long but
somewhat narrow moisture plume will bring in Pacific moisture to
the region as the cold front from the north brings in colder sub-
freezing surface temperatures on Saturday.

Rain will turn to snow as snow levels crash from well above 8000ft
near precip onset to 3000-4000ft Saturday afternoon and overnight
to Sunday over northwestern MT (5000-8000ft closer to the WY
border). Snow could fall moderate to heavy at times with increasing
wind as northerly flow at the surface intersects the terrain just
north of a tightening baroclinic zone as the front slows around
Yellowstone.

By 12Z Sunday, snow will continue over western MT as snow levels
continue to tick lower (2000-3000ft to the north and around 7000ft
closer to the WY border) due to the trough axis remaining over
western OR and northwestern CA, maintaining broad SW flow aloft
over the region.

WPC probabilities for at least 8 inches of snow through 12Z Sunday
are >50% above about 5000ft or so and >4" to about 4000ft.
Accumulating snow should reach most valley floors over western MT
by the end of this period.

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


Fracasso