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

Valid 00Z Wed Nov 03 2021 - 00Z Sat Nov 06 2021


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


Favorable setup for lake effect precipitation will continue
through Wednesday night across the Great Lakes. Cyclonic flow with
embedded shortwave troughs moving through the flow combined with
cold air advection over the warm waters will result in steepening
lapse rates. The strongest signal for lake effect snow will be
downwind of Lake Superior, northern portions of the lower
Michigan, and southwest NY off Lake Erie. Day 1 WPC probabilities
for 4 inches remain confined to the favored snow belts off Lake
Superior and northern Michigan. By Thursday into Friday, zonal
flow and less cold air advection will subside the lake effect
precipitation for day 3.


...Washington...
A parade of shortwave troughs moving through the Pacific Northwest
will bring active weather for western Washington. The first
shortwave trough pushes inland Wednesday night into Thursday
morning followed another one late Thursday into Friday. Snow
levels initially will be 7000-8000 ft and this is expected to
limit the heaviest accumulations to the highest peaks. By
Thursday, the second trough will dig deeper over the region and
with lower heights, snow levels dip to around 5000 ft. The WPC
probabilities during Day 3 for 6 inches are 30-40 percent for the
higher tops of the Olympics and WA Cascades.


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

Jackson/Taylor