Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
341 AM EST Mon Nov 21 2022

Valid 12Z Mon Nov 21 2022 - 12Z Thu Nov 24 2022

...Northwest...
Day 2...

Pacific shortwave on the leading edge of a 150kt NWly jet dives
across WA Tuesday through WA/BC Tuesday with a strong plume of
Pacific moisture ahead of a cold front. Moderate precip rates can
be expected on the western slopes of the WA Cascades Tuesday
afternoon with snow levels around 5000ft. WPC Day 2 snow
probabilities of 6 or more inches are high in the western slopes
of the WA Cascades.

For areas east of the Cascade crest, there is a risk of light
icing with surface cold air already in place over the Columbia
Basin (temps currently in the upper teens to mid 20s). Pre-cold
frontal warm air advection will make for a warm nose over the
shallow cold air. Probabilities for measurable ice is low to
moderate across the Columbian Basin.

Tuesday night, the system will continue ESE across ID. Southerly
to SSW flow ahead of the system will maximizes upslope enhancement
with snow levels dropping below 3000ft. Day 2 snow probs for 6 or
more inches are moderate over the far northern tip of Idaho into
MT ranges.

The probability of significant icing greater than 0.1" is less
than 10 percent.

Jackson