Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
334 PM EST Fri Nov 16 2018

Valid 00Z Sat Nov 17 2018 - 00Z Tue Nov 20 2018


...North and Central Rockies and Northern Great Plains/Upper
Mississippi Valley...
Day 1...

Through the overnight hours into Saturday - a mid to upper level
shortwave trough will continue to dig southeast from southwestern
Canada and the northwestern U.S.   A reinforcing shot of cold air
will sink south through the Plains, with strong high pressure
settling southeast from western Canada into the north-central U.S.
 Upslope flow along with low to mid level frontogenesis will
support a period of moderate to heavy snows extending south from
the Wyoming to the northern Colorado ranges Friday night into
Saturday.  WPC Probabilities for heavy accumulations are greatest
over the southern Absaroka, Wind River, Shirley, Laramie, Sierra
Madre and Medicine Bow mountains - indicating a Slight Risk or
greater for amounts of 8-inches or more during the Day 1 period
(ending 00 UTC Sun).   Meanwhile further to the east, low to mid
level frontogenesis along with modest upper jet forcing is
expected to support a stripe of light to moderate snows from
eastern South Dakota to southern lower Michigan.  Mesoscale
forcing may support some embedded heavier snows Friday evening
into the overnight, especially across portions of southern
Minnesota and northern Iowa into southern Wisconsin where WPC Day
probabilities indicate a Moderate Risk for amounts of 4 inches or
more.

Pereira