238
FXUS65 KCYS 031745
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1045 AM MST Wed Dec 3 2025

.KEY MESSAGES...

- Light snow will taper off by early Wednesday afternoon. Slick
  conditions will continue through the afternoon hours.

- Long term remains active with multiple systems promoting
  prolonged periods of high winds, light snow and cold but
  steadily warming temperatures.

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 253 AM MST Wed Dec 3 2025

Current observations show light snow falling across western portions
of the CWA early this morning. Radar returns support this, with
returns stretching from the Laramie Range westward to Rawlins.
Webcams along Interstate 80 show light snow accumulations, with snow
appearing to stick to the road in the Arlington area and South
Laramie Range. Per Hi-Res guidance, light snow will likely continue
through the morning hours in these areas. With snow sticking to the
road, slick morning commutes can be expected. Model and ensemble
guidance remain in good agreement regarding snowfall totals.
Additional snowfall amounts will generally be under 2 inches, with
the highest totals expected along the Interstate 80 corridor between
Cheyenne and Rawlins as northerly upslope flow continues. Snow will
taper off by the afternoon as an approaching cold front with drier
air pushes the moisture farther south.

A secondary push of colder and drier air is expected to arrive by
this afternoon. The front will push snow showers out of the area and
slowly decrease cloud cover throughout the day, but it will lock
cold air in place through Thursday morning. High temperatures today
will be in the 20s and low 30s, which is about 10 to 15 degrees
below average for early December. The cold temperatures will stick
around through the overnight hours with lows expected to be in the
teens and single digits. Valley locations like the Laramie and
Saratoga Valleys will likely be the coldest spots as clear skies and
snow cover allow for effective radiational cooling. By early
Thursday morning, most locations in the CWA will see wind chills
below zero.

Heading into Thursday, the region will return to northwest flow.
Weak disturbances aloft will move into the area, causing MSLP and
height gradients to strengthen along and west of the Laramie Range.
Winds aloft will respond and increase up to 50 kts with decent
subsidence. In-house guidance seems to think high winds at Arlington
and the South Laramie Range are likely, with over 70% probabilities
for high winds at these locations. Given that most parameters are
marginal at this time, decided to hold off on any headlines until
further model runs come out. If high winds do come to fruition, it
will likely be a longer duration event with winds continuing
throughout the day and into Friday.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Issued at 330 PM MST Tue Dec 2 2025

Long term looks to remain stuck firmly under northwesterly flow
as we see the CWA between high pressure ridging to the
southwest and several small troughs to our north to northeast,
bringing a pattern that will include breezy winds, periods of
precipitation primarily in the mountains but occasionally
spilling into the adjacent zones and high plains, and
temperatures that should very gradually warm through the end of
the period.

Ensemble clusters have been in pretty solid agreement on the
overall pattern, with primary differences lying in the strength
of the features in the long term, and small nuances in how the
ridge or troughs impact one another. Nonetheless, colder
airmasses should remain further north and east of us, allowing
the region to remain at or just below normal through the
weekend, with temperatures then becoming near to just above
normal by early next week. Meanwhile moisture will stream across
our CWA and allow for several days of precipitation that will
primarily be influenced by upslope flow into the the mountains
and produce high terrain snow, but some of this might spill
over into the adjacent valleys and down to the high plains at
times, particularly on Friday into Saturday when moisture will
be highest. Finally the low level jet will be just as active as
you would expect for December, with the 700mb flow averaging
around 50-60 knots for our wind prone locations for almost all
of the long term, and downward omega values favorable to bring
this flow to the surface, likely prompting even more high wind
warnings yet again.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1043 AM MST Wed Dec 3 2025

Snow will gradually taper off over the next few hours at KCYS
and KLAR, with a few snow showers possible near KCDR. CIGs will
remain MVFR through much of the afternoon, but should begin to
improve by the mid to late afternoon hours. Overnight, we should
start out with mostly clear skies, but there is potential for
some surface fog and/or low CIGs to develop at most terminals.
Confidence in this potential is fairly low at this time. Any
reduction in flight category should end early Thursday morning
when winds flip to westerly.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory until 11 AM MST this morning for
     WYZ110-112-114-116.
NE...None.

&&

$$

SHORT TERM...SF
LONG TERM...CG
AVIATION...MN