Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
435 AM EDT Tue Oct 22 2019

Valid 12Z Tue Oct 22 2019 - 12Z Fri Oct 25 2019

...Rocky Mountains and Northern Plains...
Days 1-3...

A clipper-type low currently over north-central British Columbia
rides a 120kt northwesterly jet streak across eastern Montana to
South Dakota through tonight. Immediately behind this shortwave
trough is a reinforcing trough that will allow amplification of a
trough down the Rocky Mountains through Thursday. Elevated
moisture from the Pacific already streaming into the northwest
CONUS ahead of these systems will allow locally heavy accumulating
snow for the higher terrain of the northern Rockies of ID/MT/WY
today then continuing tonight before shifting south with the
trough Wednesday. The leading clipper will produce a stripe of
some light warm air advection snow across eastern Montana to
southern South Dakota tonight into Wednesday.

A cold front will quickly shift south down the Front Range of WY
and CO and adjacent High Plains ahead of the amplifying trough,
reaching all the way through eastern NM and west TX by late
Thursday. Post-frontal upslope flow across the High Plains and
eastern slopes of the Rockies will couple with fairly strong
mid/upper-level jet forcing/dynamics for some locally heavy
snowfall. The focus will be over the high country of central CO
where several inches are possible through late Thursday. Some
light accumulations may spill east down along the Front Range and
Palmer Divide where a few inches of snow will be locally possible.

There is considerable uncertainty with the Day 3 forecast for the
southern Rockies and southern High Plains/Texas Panhandle. The
ECMWF/CMC/UKMET all keep the low much farther south/west than the
GFS/NAM and allow for snow to persist over NM and the TX Panhandle
through Thursday.

The probability of significant icing is less than 10 percent.

Jackson