Subj : HVYSNOW: Probabilistic He
To   : All
From : Mike Powell
Date : Tue Oct 28 2025 08:44:30

FOUS11 KWBC 280659
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
259 AM EDT Tue Oct 28 2025

Valid 12Z Tue Oct 28 2025 - 12Z Fri Oct 31 2025


....Washington Cascades...
Day 1...

A potent surface low will slowly weaken as it lifts into British
Columbia tonight. Downstream of this feature, impressively
confluent and warm mid-level flow will surge elevated PWs northeast
into the Cascades, with snow levels rising to around 8000 ft.
However, as the attendant cold front drapes into WA/OR late
tonight, it will be accompanied by falling snow levels and
impressive mid-level fgen into a deepening DGZ. This suggests that
precipitation will gradually transition from rain to a brief but
intense period of heavy snow reflected by HREF snowfall rate
probabilities peaking above 70% for 1"/hr. Snow levels falling to
around 4500 ft may actually be realized a bit lower than that due
to the intensity of this snowfall dragging down colder air, so the
higher passes such as Washington Pass will likely experience
hazardous travel. Total snowfall is likely to be generally modest,
but WPC probabilities indicate a moderate risk (50% chance) of more
than 6 inches in the highest terrain of the northern WA Cascades,
with a few inches likely at Washington Pass.

The probability of significant ice across the CONUS is less than
10 percent.

Weiss


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