FOUS11 KWBC 010623
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
223 AM EDT Fri Nov 1 2024

Valid 12Z Fri Nov 01 2024 - 12Z Mon Nov 04 2024

...Mountainous West...
Days 1-3...

Active period in the Western CONUS over the next few days
downstream of a very strong upper ridge (~99th percentile) between
Alaska and Hawaii. This will help guide several northern stream
systems into the West Coast and into the Intermountain West this
weekend into early next week. With the source region in the mid-
latitudes, moisture anomalies with each system will be modest and
thus the brunt of the snowfall will be driven by orographic upslope
into the Cascades initially then into the Rockies thereafter. Snow
levels will be on the higher side but still low enough at times to
bring some snow to the higher mountain passes.

D1 system will have the largest QPF amounts, primarily into the
WA/OR Cascades, as a cold front comes ashore. D1 probabilities of
at least 8 inches of snow are >50% above ~5000-6000ft. Into the
weekend, the lead system will move through the Great Basin with
light to moderate snow across central Idaho/western Montana and
into the Tetons southward through the Uintas and Wasatch. WPC
probabilities for at least 8 inches of snow D2 are low (<40%) in
these areas but a bit higher into the OR Cascades with the next
system quickly approaching the coast. By D3, that system will slip
through the Great Basin and into the central Rockies, with more
moderate totals possible into northern CO (Medicine Bow). Light
snow will work its way into the Front Range by the end of the
period as low pressure deepens over southeastern CO. WPC
probabilities of at least 8 inches of snow are >50% above 10,000ft
or so and for at least 4 inches are >50% above 8000ft.

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

Fracasso






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