521
FXUS65 KCYS 090541
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1041 PM MST Mon Dec 8 2025

.KEY MESSAGES...

- A long duration wind event is beginning today. While some
  breaks or lulls will occur, high winds will be a concern every
  day through Friday.

- Damaging winds are expected near and in the lee of southeast
  Wyoming mountain ranges Monday evening through Tuesday
  evening. Gusts up to 90 mph are expected.

- Cheyenne, Laramie, Rawlins, Wheatland, and Douglas can expect
  wind gusts up to 75 mph tonight into Tuesday.

- Wind gusts up to 70 mph are expected to spread into High
  Plains during the day Tuesday.

- A backdoor cold front may bring a brief reprieve from the wind
  along with a chance for snow showers Tuesday night into early
  Wednesday before winds pick up again Wednesday.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 251 PM MST Mon Dec 8 2025

The short term forecast remains on track for a high end high wind
event across nearly the entire forecast area. High Wind Warnings
this afternoon are currently in effect for the usual southeast
Wyoming wind prones of Arlington and the South Laramie Range.
Frequent gusts over 60 MPH have been occurring throughout the day
with gusts over 70 MPH popping up across the Arlington area. High
winds will continue in these zone through at least Friday, as a
stagnant upper-level pattern parks the right exit region of a 250 mb
jet streak right over the CWA.

Heading into the evening hours, the jet streak will begin to move
into the CWA, increasing winds aloft. As the night progresses, more
zones will come online into the High Wind Warning, with nearly all
zones in a Warning by 5 AM Tuesday. The biggest change in this
forecast package was the upgrade of High Wind Watches in far eastern
Wyoming and the Nebraska panhandle to Warnings. Confidence has grown
considerably in this being a large-scale impactful high wind event.
Given the parameters displayed by the GFS, this is no typical high
wind event, but definitely a higher end event. MSLP gradients will
be considerably steep, with nearly a 20 mb gradient across the CWA!
Both 850 and 700 mb CAG to CPR height gradients are nearly maxed out
with some of the highest values seen in recent memory. As a result,
winds aloft over the wind prones and wind prone adjacent areas
exceed 75 kts. High plains locations will even see winds aloft
of 60 to 70 kts! Downward omegas are also essentially "maxed
out" over the wind prones and adjacent areas as well, meaning
these strong winds will more than likely make it down to the
surface. On top of this, a strong mountain wave signature is
evident in cross sections of potential temperature and omega
fields over and in lee of the Laramie Range. Breaking mountain
waves will also ensure that these winds will make it down to the
surface.

The aforementioned parameters look to peak by mid-morning on
Tuesday, however the strongest winds are likely expected between
late morning and mid-afternoon after some mixing has taken
place. As previously mentioned, this will be no ordinary high
wind event. The wind prone areas of Arlington, Bordeaux and the
South Laramie Range could see damaging wind gusts in excess of
90 MPH. Population centers in southeast Wyoming like Cheyenne,
Laramie, Rawlins, and Wheatland could see wind gusts of 75 MPH.
Remaining high plains locations including the Nebraska panhandle
could see 70 MPH gusts. Winds will ease Tuesday evening across
most of the CWA (excluding the usual wind prones), as a cold
front pushes into the area. Winds will turn more northwesterly
behind the front, essentially shutting off high winds briefly
before another event is expected Wednesday. Aside from winds,
the cold front could bring some light snow to the area, although
accumulations are not likely outside of the mountains.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 251 PM MST Mon Dec 8 2025

The big story for the first few days of the long term, after a brief
lull Wednesday morning, will be the continuation of high winds.
Guidance is depicting, with appropriate parameters, winds ramping up
Wednesday afternoon. In the mid-levels, 700mb winds in the 55 to 66
knot range coupled with negative Omega (GFS), will help bring those
stronger winds to the surface. So, for the typical wind prone areas
across southeast Wyoming, gusts could top out around 80 mph along
the I-25 and I-80 corridors, possibly a few stronger gusts. These
stronger winds should primarily stay out of the Nebraska panhandle;
however, a couple gusts near 35 mph may make it in. These stronger
winds, diminishing slightly, will persist into and through Wednesday
afternoon/evening. By Thursday afternoon and for the remainder of
the the long term period, we are not expecting another major wind
event. However, some other changes may be in store for portions of
the CWA. An arctic front will dive south across the High Plains out
of Canada Thursday afternoon into Friday, clipping northeast
portions of our CWA. If winds diminish quicker than anticipated, the
arctic front may impact more of the CWA. So, as of now, Chadron and
Alliance will feel the brunt of this front with cooler temperatures
seeping in along with an increased threat of precipitation. In
short, highs will generally climb into the 40s and 50s while lows
dip into the 20s and 30s, and down into the teens for Chadron and
Alliance. The bulk of the precipitation associated with the arctic
front should remain to our northeast, with Chadron and Alliance
seeing the best chances of snowfall. Meager accumulations expected
in this area with generally an inch or less. Any fluctuation in the
track, accumulations could spike to near three inches. Beyond
Thursday, a 500mb ridge will slide in and as a result, weather
conditions across the CWA should become and remain relatively benign
for the remainder of the long term period.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 1040 PM MST Mon Dec 8 2025

VFR conditions expected over the next 24 hours. Winds will be
very strong, continuing to increase overnight through tomorrow
with widespread gusts in the 50-60+ knot range alongside low
level wind shear during the overnight into early morning hours
as winds ramp up aloft and then mix down to the surface. Cloud
banks at high to mid levels at SCT to BKN, but a band of
precipitation moving into the region during the last few hours
of the TAF period will bring lowered CIGs at BKN to OVC
alongside a risk of locally rain & snow, most likely at KLAR.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning until 8 PM MST Tuesday for WYZ101-104-105-
     109.
     High Wind Watch from Wednesday morning through Thursday
     morning for WYZ101-107-118.
     High Wind Warning from 2 AM to 8 PM MST Tuesday for WYZ102-108-
     119.
     High Wind Warning until midnight MST Tuesday night for WYZ103-
     107-114-118.
     High Wind Watch from late Tuesday night through late Wednesday
     night for WYZ104-109.
     High Wind Watch from Wednesday morning through Thursday
     morning for WYZ105-106-113-115-117.
     High Wind Warning until midnight MST Tuesday night for WYZ106-
     113-115-117.
     High Wind Warning until 5 AM MST Friday for WYZ110-116.
NE...High Wind Warning from 5 AM to 8 PM MST Tuesday for NEZ002-003-
     019>021-054-055-095-096.

&&

$$

SHORT TERM...SF
LONG TERM...RZ
AVIATION...CG