486
FXUS65 KCYS 012208
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
308 PM MST Mon Dec 1 2025

.KEY MESSAGES...

- A High Wind Warning has been issued for the wind prone areas
  of southeast Wyoming beginning Monday evening and continuing
  through noon Tuesday.

- A Winter Weather Advisory has been issued for the Sierra-Madre
  and Snowy ranges for Tuesday morning through Wednesday
  morning.

- Long term remains active with multiple systems promoting
  prolonged periods of high winds alongside mountain snow and
  chances of lower elevation snow as well.

- Temperatures will remain very cold through mid-week, before a
  weak warming trend arrives Wednesday onwards.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 308 PM MST Mon Dec 1 2025

We`re already beginning to see winds increase along the I-80
corridor with speeds gusting in the 50 mph range. This should
continue through Tuesday as the low level begins to set in with
speeds in the 50-65 knot range and favorable downward omega
values, alongside strong cross pressure gradients. In house
guidance also shows a high probability of high winds for our
usual wind prone locations, with high (80%) confidence overall
we`ll achieve high winds for our warned locations (Arlington,
Bordeaux, and Laramie Summit regions). Have increased confidence
in higher winds lingering across at least Bordeaux but possibly
the Summit as well, and have therefore extended these warnings
through 5 PM on Tuesday. Meanwhile as we see the current trough
push through the region and a second upper level system dig in
and strengthen across the Western US and then into the Four
Corners region, snow is expected to begin increasing for our
mountain zones beginning Tuesday morning and persist through
Wednesday morning. High res ensemble guidance paints a moderate
to high (60-70%) probability of snowfall amounts 6+ inches for
these zones, leading to good confidence in at least advisory
level accumulations, and a Winter Weather Advisory has been
issued from 5 AM Tuesday through 11 AM Wednesday for this. And
while snow is expected to spill over into the adjacent zones and
some of the high plains, shadowing should keep the bulk of this
from being impactful, with only a dusting to around 1-2 inches
for adjacent zones primarily along the I-80 corridor. Finally,
the fresh incoming snow alongside already fallen amounts with
the breezy winds will bring a threat of blowing snow, and have
continued this in the grids impacting mountain and adjacent
zones including into the I-80 area.

Otherwise look for a slight warmup on Tuesday as temperatures
reach closer to near normal for this time of year, but a cold
airmass with the second system will help to drop us right back
down with highs stuck below freezing again on Wednesday.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Issued at 308 PM MST Mon Dec 1 2025

Mean northwest flow aloft looks to persist through the period with
hints of shortwave ridging intermittently putting a damper on what
seems to be near daily snow chances across the Snowy and Sierra
Madre ranges. Current ensembles and clusters paint this picture well
with a shortwave ridge both on Thursday and Monday passing within
the vicinity of the forecast area though slight variations exist in
the amplitude and track that could impact the nightly radiational
cooling potential (Thursday AM lows in the single digits to teens).
After a chilly Thursday morning highs climb back near freezing in
the afternoon.

High winds look to return Friday after a quiet few days wind-wise
Wednesday/Thursday with the in house guidance showing a greater than
60 percent chance for high wind criteria in the typically wind prone
areas. This is expected to be a long duration event with the 700mb
jet between 45-55kts per clusters and a tightening pressure gradient
working to get these winds to the surface. At the same time things
look to turn wintry once again by Friday afternoon in the mountains
with several inches likely in the Snowy and Sierra Madres through
Sunday as more shortwave activity brings moist flow to the higher
elevations. However once again shadowing effects are likely going to
limit how much accumulation we can produce outside of the high
terrain. Near average temperatures continue into the weekend as we
feel the impact of ridging (and the embedded shortwave activity on
its eastern periphery producing the snow) keeping highs in the 30s
and 40s through the weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1044 AM MST Mon Dec 1 2025

Mostly VFR conditions expected over the next 24 hours. The one
exception will be KRWL where snow could bring reduced
visibilities towards the end of the TAF period. Otherwise,
expect skies to be clearing today with high to mid level clouds
returning tomorrow with the next incoming system. Winds breezy
today with gusts in the 20-35 knot range, strongest at KRWL,
with conditions lessening overnight into tomorrow. As our next
system approaches tomorrow, we`ll see some wind shear primarily
impacting KCYS and KBFF during the morning hours.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning from 8 PM this evening to 5 PM MST Tuesday
     for WYZ106-116-117.
     High Wind Warning until 8 PM MST Tuesday for WYZ110.
     Winter Weather Advisory from 5 AM Tuesday to 11 AM MST
     Wednesday for WYZ112-114.
NE...None.

&&

$$

SHORT TERM...CG
LONG TERM...TT
AVIATION...CG