683
FXUS65 KCYS 232330
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
430 PM MST Sun Nov 23 2025

.KEY MESSAGES...

- High Wind Warnings have been issued for the wind prone areas
  of southeast Wyoming Monday through Tuesday AM.

- A strong cold front will bring a chance for a few light snow
  showers Monday night followed by daytime wind chills in the
  teens and 20s on Tuesday.

- The probability of an arctic cold front is increasing for next
  weekend. Very cold temperatures and accumulating snowfall
  remain possible.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 230 PM MST Sun Nov 23 2025

The area is enjoying another day of unusually pleasant weather for
this time of year with temperatures largely in the 50s to low 60s,
light winds, and mostly clear skies. Temperatures have been running
several degrees warmer than forecast, thanks to deeper than
anticipated mixed boundary layers. This also has lead to lower than
forecast dewpoints. While current satellite imagery depicts clear
skies over the majority of the area, a thicker cloud shield
associated with a strong upper level closed low is apparent just to
our south, circulating over east central Colorado. This system will
slowly move northeast through early Monday, bringing more cloud
cover over our southeastern zones overnight. However, this system
has taken a last minute jog to the east, which has lead to high-res
models backing off on rainfall potential dramatically for our area.
As a result, PoPs were decreased significantly with this update, and
are now confined mainly to just Cheyenne, Kimball, and Morrill
counties. A few high-res models even keep rainfall out of our area
entirely. Still, a mention of showers is retained for these areas,
as Sidney will be right on the edge of a very narrow TROWAL on the
backside of this system.

Once this upper level low rejoins the main flow aloft to the north
on Monday, expect to see a rapid rise in pressure gradients across
the area, and thus a rapid increase in wind speeds as westerly flow
resumes aloft. The threat for high winds in the wind prone areas
will increase proportionally Monday into Monday night. This looks
like more of a large-scale driven wind event, with all common high
wind parameters at least marginally supportive of strong winds. 700-
mb winds are perhaps the strongest signal with this event (as
typical height/pressure gradient signals are more marginal), showing
fairly widespread 50 to 60 knot winds developing over southeast
Wyoming by Monday evening. These peak during the late evening hours,
just ahead of a strong surface cold front expected to punch through
around midnight. LREF median 700-mb winds exceed 50-knots over the
wind prone areas. This gives enough confidence to upgrade the
existing High Wind Watches to Warnings, but the timing was adjusted
slightly for this update. The Arlington/Elk Mountain area will
likely be first to see high winds, with internal probabilities
pushing above 50% by 8AM Monday. The I-80 summit area will likely be
a little slower, so pushed the start time back to noon. While
confidence is medium to high in the I-80 wind prone areas seeing
gusts over 60 mph, confidence is lower for the I-25 wind prone
areas. Lower altitude (i.e. 750-mb or 800-mb) height gradients and
wind speeds are not as impressive as those at 700-mb which reduces
confidence for lower elevation wind prone areas. Still, the strong
winds aloft and marginally supportive MSLP gradients were enough to
still upgrade the Bordeaux area, but with a shortened time period.
Winds will likely be slower to arrive here, and then the potential
will drop off quickly once the winds turn northwest behind the
surface cold front, around midnight. A few rogue gusts cannot be
ruled out for areas outside of the typical wind prone areas,
particularly along the frontal boundary Monday evening, but
confidence is much too low to expand the High Wind Warning any
further. Still, look for a breezy (and rather warm) day Monday
across most of southeast Wyoming.

Much to the dismay of our paltry early season mountain snowpack, the
system associated with Monday night`s cold front will take a track
that is rather unfavorable for widespread precipitation. The low
pressure center should remain just north of the area, putting most
of the area in dry, northwest downslope flow. Some limited mid-level
moisture along and just behind the front may produce a few scattered
snow showers during the late evening and early morning hours, mainly
confined to Converse/Niobrara counties and the higher
mountains. This could extend into the Wheatland/Chugwater area,
which often develops a terrain-induced convergence zone in
northwest flow wind events. Lots of dry air in the forecast
soundings will limit snowfall rates, such that a dusting to an
inch at most is the most probable scenario (if any snow falls at
all). Probabilities for 1" of snow are less than 10% for all
except the highest mountain peaks.

Conditions will remain windy across the area Tuesday behind the cold
front, but the threat for high winds will decrease as the best
synoptic forcing shifts to the northeast. Still, this will finally
give the area a taste of winter cold temperatures, with highs mostly
in the 30s and brisk northwest winds gusting 40+ mph keeping wind
chills in the teens to mid 20s at the warmest. Winds will finally
decrease Tuesday evening, but the break may be short-lived.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 230 PM MST Sun Nov 23 2025

As the system departs the Intermountain West on Tuesday, A
ridge begins to strengthen over the Western coastline of the
United States. This will put us in northwest flow through
Thursday. While in northwest flow from being on the leading edge
of the ridge a weak shortwave passes through the region. This
shortwave looks to squeeze the 700mb pressure gradient allowing
for a 700mb jet develop. While there is a little uncertainty as
to the overall strength of this jet, so models are depicting the
potential for another high wind scenario for our wind prones.
The GFS (which does a little better with mountain winds) has the
wind speeds around 55 knots with some isolated accelerations up
to 60 knots then backing down to 40 knots by 00z Thursday. The
Euro doesn`t depict the gradient tightening as much resulting in
slightly weaker continuous jet of winds between 35 to 40 knots
Wednesday and Thursday. There is also a plume of moisture that
the models have continued to trend that accompany this
shortwave. However due to the surface winds being the westerly
and northwesterly downslope flow no precipitation is expected
for region except maybe the Sierra Madre mountains despite the
increased cloud cover. No significant weather is expected
through Friday. However, this weekend the pattern will flip once
again. A broad reinforcing trough looks to set up over the
Western half of the United States. This trough will drag cold
arctic air from Canada by means of an arctic front through the
Intermountain West. There are a few disagreements with how this
trough will become established but each model depicts 700mb
temperatures dropping to around -20C. These colder temperatures
will translate to our daily highs being in the 20`s and 30`s and
our overnight lows dropping into the low teen`s and single
digits. The GFS has the colder air staying over us through
Tuesday while the Euro has "warmer" temperatures around -7C by
Monday. The primary difference is the Euro depicts this quasi-
thermal ridge setting up on Monday and ultimately cutting off
the low pressure system near Southern California from the flow.
However, the GFS keeps the depth of the trough the same and
progresses that system across the southern half of the United
States. Ultimately the depth of the trough will determine how
long the arctic air will reside over the region and effect how
fast the Intermountain West recovers back into the "warmer"
temperatures.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 430 PM MST Sun Nov 23 2025

Ceiling heights are going to remain above 10,000ft through
tonight. Between 06z and 10z some showers look to move over
KSNY. The models continue to push the system further east. Now
its uncertain if KSNY will receive rain but still put showers in
a PROB30 group between 06z and 08z. With the exception of KSNY
all terminals are expected to remain dry over the next 24 hours.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning from noon Monday to midnight MST Monday
     night for WYZ106.
     High Wind Warning from 8 AM Monday to 5 AM MST Tuesday for
     WYZ110.
     High Wind Warning from noon Monday to 5 AM MST Tuesday for
     WYZ116-117.
NE...None.

&&

$$

SHORT TERM...MN
LONG TERM...MM
AVIATION...MM