FOUS11 KWBC 260825
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
425 AM EDT Sat Oct 26 2024

Valid 12Z Sat Oct 26 2024 - 12Z Tue Oct 29 2024


...Pacific Northwest...
Days 2-3...

Upper level ridging will give way to a broad upper trough, carved out
by a series of shortwaves moving south of a low moving into British
Columbia. This will support the return of unsettled weather and
falling snow levels in the wake of a strong cold front moving from
the Northwest into the northern Rockies on Sunday. Strong mid-to-
upper level forcing and a shot of deeper moisture are expected to
generate some of the heaviest precipitation across western Washington
and Oregon Saturday night into Sunday morning. However, with snow
levels above 6000 ft in most locations, winter weather impacts will
be limited, initially. Snow levels are expected to steadily drop
through Sunday, dipping to around 4500-5000 ft along the Washington
and Oregon Cascades by Monday morning. Conditions will remain
unsettled as onshore flow persists. WPC probabilities indicate that
most significant snow accumulations will remain above the major
Washington and Oregon passes through Monday Morning.

Unsettled weather will continue across the Northwest through
Monday, with snow levels dipping further as additional shortwaves
move through the base of the broader scale trough as its axis
shift inland. WPC probabilities indicate that potentially
impactful accumulations will become more likely along the Oregon
Cascades, with probabilities for accumulations of 4 inches or more
climbing above 50 percent in some of the passes.

Snow will also be spreading south into the Sierra Nevada and east
into portions portions of the northern and central Rockies Monday
into Tuesday. The highest probabilities for significant
accumulations through Tuesday morning center over north-central
Idaho and southwestern Montana and northwestern Wyoming -- in and
around Yellowstone NP. WPC guidance shows at least low
probabilities for accumulations of 6 inches or more in the higher
elevations of these areas.

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

Pereira


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