Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
442 PM EDT Mon Apr 13 2020

Valid 00Z Tue Apr 14 2020 - 00Z Fri Apr 17 2020

...CO to Southern High Plains...

Day 1...
A reinforcing trough currently pushing southeast through Wyoming
will shift east across the central Plains tonight. Surface high
pressure following this trough will continue to promote an
easterly upslope flow for the eastern slopes of the CO Rockies
into tonight while the left exit region of a strong westerly jet
over Texas will promote lift to spread across the southern High
Plains (OK/TX Panhandles) and into southwestern OK tonight. Light
to moderate snow, and low chances for four or more inches are
across the Palmer Divide in CO and over southeast CO and the OK
Panhandle for Day 1. Should any accumulating snow make it to OKC
it would the first instance of this since April 1989.


...Central Appalachians...

Days 1-2...
The reinforcing trough that ejects east across the central Plains
tonight reaches the Ohio Valley on an increasing jet streak
Tuesday afternoon. Continental air is lifted over the central
Appalachians with snow levels generally around 2000ft, dropping to
1000ft Tuesday night. Moderate snows are expected at these
elevations across the Allegheny Plateau in eastern WV and western
MD as well as the higher ridges east including the Blue Ridge in
central/northern VA. Day 1.5 snow probabilities are moderately for
four or more inches across the high terrain.

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

Days 2-3...
Another reinforcing trough drops south down the Canadian Rockies
Tuesday, pushing across western MT Tuesday night and amplifying
southwest to the northern Great Basin Thursday. Broad cyclonic
flow across the western U.S. with Pacific-sourced and eventually
Gulf of Mexico sourced moisture promotes snow across the northern
Rockies Tuesday night/Wednesday. Day 2 snow probabilities for 6 or
more inches is high across western MT/northern ID and northwest
WY. These high probabilities spread to southern WY and northern CO
Wednesday night/Thursday with Day 3 probabilities moderately high
for 6 or more inches spilling onto the Central High Plains of
southeast WY/northeast CO and across the NE Panhandle.


For Days 1-3, the probability of significant icing (0.25 inch or
greater) is less than 10 percent.

Jackson