932
FXUS65 KCYS 301200
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
500 AM MST Sun Nov 30 2025

.KEY MESSAGES...

- A winter weather advisory will go into effect for the Sierra
  Madre and Snowy mountains Sunday morning for snow
  accumulations up to 10 inches.

- A High Wind Watch has been issued for the wind prone areas of
  southeast Wyoming beginning Monday evening.

- Very active long term forecast expected with multiple troughs
  moving through and promoting snow chances.

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

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 310 AM MST Sun Nov 30 2025

Current observations across the area show a very cold night with
temperatures now around 10 below zero over portions of east
central Wyoming and western Nebraska. Light surface snow pack
and clear skies/light winds for much of last night has provided
suitable conditions for temperatures to bottom out to near
record low temperatures. Chadron destroyed their previous record
of -1 yesterday, set in 1985, with a low of -9. Expect a few
other record lows to be met early this morning. Further west,
thick cloud cover is spreading eastward ahead of the next
clipper-like system. This cloud cover has resulted in
temperatures remaining in the single digits and low teens across
much of southeast Wyoming...so expect temperatures to climb
slowly for the rest of the morning ahead of the next fast moving
clipper. The same will likely happen to western Nebraska as the
cloud shield will be over Chadron and Sidney before sunrise.

Not much of a break today as models show the clipper digging
southeast into Utah and eventually Colorado by this evening.
Synoptic models continue to struggle with the impacts of this
system and show hardly any snowfall. However, these models
traditionally don`t do well with overrunning/WAA aloft along
arctic boundaries...which is what we`re facing today and
especially this evening. High res guidance (HRRR, NAMNEST) and
short range ensembles show a different story, with persistent
snowfall across much of southeast Wyoming beginning late this
morning and continuing through this evening. Although snowfall
is expected to be pretty light, high res guidance shows some
moderate snow banding along I-80 as the upper level vort max
gets close to the Wyoming border. Normally, this isn`t too much
of a concern, but ground temperatures will support snow
accumulation through much of the day with forecast highs only
in the low to mid 20s at best, and hardly any breaks in the
cloud cover. Continued to increase POP across the area...and
even extended mention of snowfall well into western Nebraska
with the HRRR showing widespread light snowfall until midnight
tonight. Kept the Winter Weather Advisory going for the
mountains with a solid 6 to 10 inches of snow. May need to
extend this Advisory into the lower elevations and I-80 Summit
area today if snowfall rates are higher than models currently
suggest. However, current snow accumulations are a little shy of
3 or so inches, so will keep them out of the Winter Weather
Advisory for now. Further east, can`t rule out snow
accumulations of over 2 inches, but confidence is pretty
low...so just nudged snow accumulations up slightly and extended
them further east past the I-25 corridor. Remaining cold
tonight with lows back into the single digits in periods of
light snow and/or flurries through midnight. Expect some
clearing towards sunrise Monday, so low temperatures may trend
lower with any surface snowpack.

Attention then shifts to winds and possible blowing snow on
Monday and Monday night. Once Sunday`s clipper system moves east
of the area, another disturbance will quickly dig south into
the Pacific NW, Idaho, and Montana. This system will have a
strengthening upper level as it moves southeast. All models show
low to midlevel pressure gradients responding with increasing
700mb subsidence along the spine of the mountains. The GFS, NAM,
and Canadian all show 700mb winds increasing over 60 knots by
early Tuesday morning...which is a clear upward trend compared
to previous model runs. In-house wind guidance shows increasing
probabilities, especially near the Arlington/Elk Mountain area,
with values as high as 90%. With this in mind, issued a High
Wind Watch starting Monday evening for the I-80 corridor
including Arlington...with the I-80 Summit and foothills and the
Bordeaux area along Interstate 25 starting a few hours later at
800 PM local time. In-house wind guidance shows the potential
for 70+ MPH winds at Arlington, so went more aggressive with
that zone compared to the others. In addition, some surface snow
pack is expected which may lead to blowing snow concerns in a
few of these High Wind areas. This will depend on a few factors,
including snow depth and timing of the strongest winds. Monday
is expected to be warmer, with highs in the 30s and low 40s. How
much this influences a light snowpack is unclear, but will add
some blowing snow to the forecast for Arlington/Elk Mountain to
start out. Kept the High Wind Watch valid through Tuesday
evening for the Arlington area since the low level pressure
gradient will struggle to weaken.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Issued at 321 PM MST Sat Nov 29 2025

Long term remains active as we see a system bring gusty winds
and precipitation chances to start the period, followed by a
brief dry period alongside some warming to bring us back to near
normal temperatures, but another approaching system at the end
of the period will cause another potential high wind event
alongside increasing precipitation chances once again.

Into Tuesday, as the trough starts to move into the region,
precipitation overspreads with temperatures also cooling thanks
to the passing cold front. Expect as precipitation moves in
later Tuesday through Wednesday, we should be cold enough at all
levels to promote snowfall, but without a strong amount of QPF,
overall accumulations should be fairly light - a few inches for
the mountains, and around an inch or less for lower elevation
locations, with some locally heavier amounts not out of the
question and windy conditions promoting blowing snow and some
locally high drifts.

Temperatures on Wednesday remain widespread at our below
freezing for highs, but expect a gentle warming trend thereafter
with highs warming into the 30`s to 40`s by Friday. The region
will dry out on Wednesday, but Thursday into Friday we should
see a return of light to occasionally moderate mountain snow
thanks to upslope flow. And on the note of our flow pattern,
models continue to indicate we`ll be seeing our next high wind
event Friday into Saturday with the approach of our next trough,
with in house guidance already peaking into the 60-80%
probability range for our wind prone locations. While overall
active, overall current forecasts suggest our most impactful
conditions will remain the region`s usual high winds as we move
into the start of December.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 500 AM MST Sun Nov 30 2025

Another fast moving clipper is expected to push into the area later
today and tonight. Clouds will gradually lower through the day with
snow expected at all southeast Wyoming terminals, with snow possible
for western Nebraska by this evening.

HAZARDS/WEATHER TRENDS: VFR conditions will continue early this
morning with CIGS gradually lowering through 15z. MVFR conditions
and light snow expected for KRWL, KLAR, and KCYS between 17z and 23z
this afternoon with periods of IFR possible...most likely at KRWL.
Lower confidence forecast for the western Nebraska terminals, so
kept VFR conditions through 00z Monday with some snow possible
through late this evening through 06z.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...

WY...High Wind Watch from Monday evening through Tuesday morning
     for WYZ106-116-117.
     High Wind Watch from Monday afternoon through Tuesday evening
     for WYZ110.

     Winter Weather Advisory from 11 AM this morning to 5 AM MST
     Monday for WYZ112-114.

NE...None.

&&

$$

SHORT TERM...TJT
LONG TERM...CG
AVIATION...TJT