Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
430 AM EDT Tue Mar 26 2019

Valid 12Z Tue Mar 26 2019 - 12Z Fri Mar 29 2019


...Pacific Northwest/Northern California to the Northern Rockies
and Adjacent High Plains...

A deep upper low centered near 45N/134W is forecast to drift
slowly east toward the Pacific Northwest over the next few days. 
Widespread heavy amounts are not expected through the Day 1 period
(ending 12Z Wednesday).  The threat for heavy snow is forecast to
increase across the northern Sierra by late Wednesday as a
well-defined shortwave moving south of the low moves into
California along with a second front and deeper plume of moisture.
 With the onshore winds waning, the threat for heavy snow is
expected to diminish along the Sierra as early as late Day 2. 
However, with shortwave energy lifting northeast, increasing
divergent flow aloft, along with low to mid level frontogenesis
are expected to raise the threat for heavy snows across portions
of the northern Rockies.  WPC Day 3 probabilities (ending 12Z
Friday) indicate a Moderate Risk for accumulations of a foot or
more for portions of the southwest Montana ranges with a risk of 4
inches and 8 inches eventually spreading out over the Plains
adjacent to the northern Rockies late Thursday night/early Friday
morning as the system continues eastward.

Bann