Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
441 AM EDT Tue Nov 02 2021

Valid 12Z Tue Nov 02 2021 - 12Z Fri Nov 05 2021


...Colorado...
Day 1...

A shortwave trough amplified as it moves across CO today producing
modest height falls within a confluent moisture stream to produce
periods of moderate to heavy snow, generally above 7000 ft in the
CO Rockies. Day 1 WPC snow probabilities are around 30 percent for
6 or more inches in the north-central CO ranges.

...Great Lakes...
Days 1-2...

Persistent cyclonic flow and further cold air advection across the
Great Lakes through Wednesday will produce a favorable environment
for lake effect snow through the next two days. The heaviest snow
is expected today off Lakes Superior and northern portions of
Michigan which has the strongest cold air advection with the main
shortwave trough passage which leads to the steepest lapse rates
and highest inversion depths. Day 1 WPC snow probabilities are
likely for 4 or more inches across the main snow belts of the UP
and northern LP. The trough re-orients itself to the west leading
to more neutral advection and a lower probability for lake
enhanced precip by Wednesday night.


...Washington...
Days 3...
Back-to-back troughs Wednesday night and Thursday night through
Friday continue an active weather pattern for western WA. While
snow levels around 7000ft limit snow to the highest peaks on
Wednesday night into Thursday, snow levels fall behind the trough
passage on Thursday, dipping below 5000ft Thursday night as
moisture ahead of the next trough arrives. Day 3 WPC snow
probabilities are moderate for 6 or more inches over the higher
Olympics and WA Cascades.


For Days 1-3, the probability of significant icing is less than 10
percent.

Jackson