FOUS11 KWBC 080623
QPFHSD

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


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