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FOUS11 KWBC 180655
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
255 AM EDT Sat Oct 18 2025

Valid 12Z Sat Oct 18 2025 - 12Z Tue Oct 21 2025


...Pacific Northwest and Northern Rockies...
Days 1-2...

A fairly amplified yet progressive pattern will take a strong
Pacific low pressure system into British Columbia tonight in a
weakening state. Its attendant cold front will promote a modest
atmospheric river of moisture into the Pacific Northwest starting
later this morning and progressing west to east into the northern
Rockies tonight. Snow levels will start quite high as QPF
increases, favoring the high Cascades initially. The cold front is
forecast to come ashore coastal WA around 06Z Sun and usher in
colder air aloft as snow levels crash to around 4500-5500ft (north
to south) along the WA Cascades as QPF rates decrease. However,
this will bring accumulating snow to the higher passes (e.g.,
Washington Pass/SR-20, elevation 5477ft) before moisture moves out
of the region around Monday morning. Into the northern Rockies,
snow levels around 6000-8000ft will fall to around 5000ft as snow
winds down later on Monday. The Bitterroots, Lewis Range, Absaroka,
and Tetons are forecast to see minor-to-moderate snowfall amounts
though some areas in NW MT may see over a foot (esp above 7000ft).
WPC probabilities for at least 8 inches of snow days 1-2 are >50%
above 5500ft or so and "plowable" snow (~2") down to around 4500ft
in the WA Cascades.


The probability of significant freezing rain across CONUS is less
than 10 percent.


Fracasso

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