Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
433 AM EDT Sun May 05 2019

Valid 12Z Sun May 05 2019 - 12Z Wed May 08 2019


...Northern Rockies and northern High Plains...
Day 1...

Weak shortwave troughs embedded within northwest flow cross MT
through tonight. Lift from these disturbances and the surface
stationary front in the lee of the northern Rockies allows
continued accumulating snow across north-central MT and higher
elevations of northern WY. Moderate to high Day 1 probabilities
for four inches are across these areas. The primary shortwave
trough axis crosses MT late tonight with precip shifting southeast
ahead of the axis, bringing an end to MT snow early Monday.


...Intermountain West...
Days 1-3...

Closed low pressure reaches the central CA coast today and stalls
there through tonight before shifting east across the Desert SW
and opening into a trough Monday through Tuesday night. Pacific
moisture spreads cyclonically ahead of the system across Baja CA
and into the Four Corners today through Tuesday, priming the area
for heavy precipitation and high snow elevations. Snow today
should be limited to highest Sierra Nevada mountains directly
ahead of the low and more for the same areas on Day 2 as the low
tracks south of the Sierra Nevada.

The upper level trough axis shifts east across The West Tuesday
and Tuesday night with snow elevations 8000 to 9000ft across the
Intermountain West with a gradient across WY and northern WY
having a 6000 to 7000ft snow elevation. Day 3 probabilities for
six or more inches area focused on the highest WY mountain ranges
with the highest terrain in UT/CO also having some low to moderate
probabilities for six inches.



The probability of significant icing is less than 10 percent for
Days 1-3...

Jackson