Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
330 AM EDT Fri Apr 19 2019

Valid 12Z Fri Apr 19 2019 - 12Z Mon Apr 22 2019

...The Mountains of south central to southwest MT south across Wy
and central CO...

Days 2-3...

A shortwave dropping slowly along the WA/OR coast Saturday will
drift onshore California and into the Great Basin on Sunday.
Associated with this feature, the ECMWF shows a 300 mb jet maxima
crossing northern MT.  Increasing diffluence within the right
entrance region to this jet supports divergence maxima aloft over
the ranges of southwest to south central MT, then extending across
the border into WY.
The low level convergence and moisture convergence ahead of the
700 mb front leads to accumulating snow in these mountains, with
several inches in favored upslope areas possible.  Amounts
increased over yesterday's forecast due to a slowing trend in the
front moving through.

On day 3 Sun,  the 700 mb front drops south out of CO and into CO.
The combination of lift along the frontal boundary and enhanced
moisture and 700 mb convergence focuses a period of extending out
of the front ranges in eastern WY across the front range in
central CO.  Several inches are possible on day 3 in the the WY
Tetons/Absaroka Mountains, and the Bighorns before ending and
moving down into the front range of CO, where the 00z ECMWF has a
burst of ascent centered on Sun evening. 

The probability of significant freezing rain is less than 10
percent Days 1-3.

Petersen