963 
FXUS65 KCYS 162147
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
247 PM MST Wed Dec 16 2020

.SHORT TERM...(This evening through Thursday morning)
Issued at 244 PM MST Wed Dec 16 2020

Minor wave action in clouds have decreased over the course of the 
morning and early afternoon hours as overall clearing is expected 
more this afternoon and into the evening. While winds have decreased 
some persistent gusts into the upper 40s and low 50s have been the 
case last few hours to warrant keeping the headline ongoing as model 
gradients by both the NAM and GFS hint at possible quick resurgence 
of high winds possible just around sundown as they have solutions of 
additional clearing. Craig to Bordeaux gradients remain in the 50-60 
meter range at 850mb but with lagging support above, hard to support 
continuation beyond current expiration of 8 PM MST. 

Some minor snowfall accumulation of around an inch was reported by 
several observers out near Elk Mountain and Rock River to include 
and prolong the duration of blowing snow that has been hampering web 
cams and road conditions along I-80. As the ejecting shortwave moves 
out into the Plains looking at some minor accumulation still being 
on track for the southeastern mountains with minor accumulation of 
under 5 inches expected in next 12 hours, mainly on the higher 
peaks. 

Lows tonight under clearing skies expected to drop back into the 
middle to upper teens for many with the little to some snowpack 
areas being a touch warmer in the low 20s. 

.LONG TERM...(Thursday through Wednesday)
Issued at 244 PM MST Wed Dec 16 2020

High pressure continues to build eastward across the four corners, 
while low pressure strengthens over the Southeast with the 
associated cold front extending through Alabama.  

Conditions are expected to become unstable as an upper level ridge 
propagates eastward towards the Midwest.  This will allow a series 
of shortwaves to slowly push east through the CWA Thursday evening, 
followed by a positive tilted trough axis at 500 mb extending from 
the Upper Midwest through the Upper Colorado Basin. Temperatures 
will begin to trend downward with a high 33 degrees on Friday. 
Models are in fairly good agreement with snow showers beginning 
Thursday night through mid-morning Friday.  Higher snow amounts are 
expected along the Sierra Madres with storm totals of 6 inches or 
higher on the taller peaks. In additions, west of Laramie will see 
around 1 to 2 inches of snow with lesser amounts to the east.

Into the weekend, upper level ridging is expected to build back into 
the region and remain through early next week. Main concern through 
the weekend will be potential wind events. Strong subsidence over 
southeastern Wyoming appears to have strengthened in the models, 
with Craig to Casper gradients hovering around 55 meters on Thursday 
afternoon, and greater than 70 meters Saturday into Monday. 

Heading into the middle of next week, long range models suggest an 
upper level trough digging east/southeast through Wyoming into the 
Nebraska Panhandle.  Combined with some moisture at the surface, 
provides a chance for snow showers wednesday morning in southeastern 
Wyoming.


&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1029 AM MST Wed Dec 16 2020

Latest satellite shows an area of wave clouds as ongoing strong
winds are possible so lingering concerns for some wave action and
possible turbulence on approach or takeoff possible. Winds will
begin to diminish as clouds disperse later this afternoon and
early evening. MVFR conditions likely to last a few more hours at
KRWL as clouds are expected to disperse this afternoon. Otherwise
VFR conditions for remaining terminals and gusty winds this
afternoon. 


&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning until 8 PM MST this evening for WYZ106-110-116-
     117.

NE...None.
&&

$$

SHORT TERM...WM
LONG TERM...MD
AVIATION...WM