Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
440 AM EDT Mon May 06 2019

Valid 12Z Mon May 06 2019 - 12Z Thu May 09 2019


...Northern and Central Rockies onto the High Plains...

Southern stream low pressure shifts east from the central CA coast
today and opens Tuesday and Tuesday night as it pushes east across
AZ/NM as a trough. A northern stream shortwave trough moves
southeast across the Northern Rockies Tuesday, interacting with
the remnant southern stream trough on Wednesday over the central
Rockies. Ample Pacific and Gulf moisture with this system warrants
a heavy snow threat, despite high snow elevations of 8000 to 9000
ft in UT/CO. A stationary front along a baroclinic zone allows for
lower and perhaps heavier snow over WY and southern MT. Day 2
probabilities are moderate to high for six inches over portions of
the Absaroka and Wind River Ranges in WY and low to moderate for
the high Sierra Nevada Uinta and CO Rockies.

Amplifying northeasterly flow on the backside of a low level wave
dropping southeast across WY into northeast CO will help support
some locally heavy amounts. Snows will continue along portions of
the Wasatch and Uinta Mountains in UT while spreading farther east
into CO, with significant accumulations possible for portions of
the Sawatch and San Juan Mountains. Developing upslope flow west
of a low spinning up over the High Plains will begin to produce
snow east of the Divide along the Front Range on Wednesday.
Moderate to high Day 3 probabilities for six inches are across the
CO Rockies. The northern end of the northeasterly flow in the
Dakotas should be cold enough for snow in western SD/NE with low
probabilities for two inches over the NE Panhandle and the Black
Hills on Day 3.

The probability of significant icing is less than 10 percent.

Jackson