Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Thu Apr 18 2019

Valid 12Z Thu Apr 18 2019 - 12Z Sun Apr 21 2019


The next storm system will reach the Pacific Northwest Friday and
move onshore and inland over the weekend.  The 00z GFS shows a
forming 700 mb low and front crossing
ID into southwest MT and WY. Falling heights correspond with
falling temperatures aloft.  Enhanced moisture in the frontal zone
and low level convergence lead to ascent, which in turn is
orographically aided Sat night. Snow levels should fall from
around 9000 ft to 7000 ft across the Absaroka, Teton, and Bighorn
Ranges, resulting in accumulating snow. WPC probabilities show a
Moderate to High Risk for 4 inches and Low to Moderate for 8
inches or more across these ranges on Day 3, ending 12z Sunday. 
Only modest timing differences with the front exist across WY Sat
night.

The probability of significant freezing rain is less than 10
percent.

Petersen