532
FXUS65 KCYS 241107
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
407 AM MST Mon Nov 24 2025

.KEY MESSAGES...

- A High Wind Warning if in effect for the typical wind-prone
  regions of southeast Wyoming through early Tuesday morning.

- A High Wind Watch has been issued for northern portions of the
  Nebraska Panhandle from 8PM tonight through 2PM tomorrow.

- 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 TUESDAY NIGHT/...
Issued at 153 AM MST Mon Nov 24 2025

Mostly clear skies across the central portion of the CWA tonight
with residual clouds from the departing system currently over Sidney
and the southeastern Panhandle, with some high-level clouds moving
into northern locations. Light winds everywhere, with temperatures
currently sitting in the teens to 30s. The I-80 corridor east of the
Laramie Range is the warmest spots tonight as clouds have been
slower to decay overnight.

The upper-level low will continue its trek of to the northeast and
into the Midwest tonight, with weak, brief ridging moving overhead.
The ridging will be short-lived as the next upper-level trough
begins to push into western regions by 21Z today. The trough will
slowly propagate west to east across the CWA this afternoon and into
the overnight hours. The strongest 500mb cyclonic vorticity
advection will remain largely out of the region, but the northern
zones of Converse and Niobrara counties could see the southern
extend of the swath of strongest CVA tonight. There will be three
primary facets to this system that occur throughout the day today.
The first will be strong winds at the wind-prone region as a 700mb
low dips into the northern CONUS from southern Canada. This low will
strengthen height gradients across the Laramie Range, resulting in a
60 to 65kt jet overhead. Strong downward omega fields are projected
within the GFS, suggesting that these strong low-level jet winds
will be able to mix down to the surface, resulting in gusts between
60 and 70mph, depending on location. High Wind Warnings are in
effect for the typical wind-prone regions of southeast Wyoming.

The second facet of this system will be the increasing precipitation
chances ahead of, and behind, the passing cold front. Northern zones
that see the strongest 500mb CVA later today are the same regions
favored for increasing precipitation chances, about 25 to 35%
chance. Any precipitation that occurs in the northern-most zones
will start as cold rain before quickly transitioning to a rain/snow
mix then finally into pure snow. Significant accumulations are not
expected, less than an inch for most locations. Snow with this
system is the result of the third facet: a strong cold front
dragging through the region. Along and behind this front, strong
winds and precipitation are expected across the northern zones.
Temperatures are Tuesday will be between about 15 and 25 degrees
cooler than high temperatures for Monday, leading to the first real
winter-like temperatures. 700mb temperatures will tank into the -12
to -10C range with the front, further supporting a very cold day
Tuesday and even colder start to the day Wednesday, with morning
lows in the teens and 20s.

As this system begins to work its way through the region, the 700mb
low will strengthen significantly across western South Dakota Monday
night into the early Tuesday morning hours. With a strong cold front
and deepening low, very strong 800 and 850mb winds are expected
across the western Nebraska Panhandle. The 800mb jet will peak
between 60 and 65 kts over Dawes County early Tuesday morning, with
the 850mb winds peaking around 50 to 55 kts during the same time.
With decent downward omega values suggested by the GFS, went ahead
and issued a High Wind Watch for the northern Nebraska Panhandle, as
gusts up to 60mph ahead of and behind the cold front cannot be ruled
out. Considered including Niobrara County in southeast Wyoming into
this Watch, but not all the variables were there to support a High
Wind Watch issuance. Will let day crew take another look and make
the final decisions on whether or not an upgrade is needed and if
Niobrara County should be included.

&&

.LONG TERM /WEDNESDAY 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 /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 407 AM MST Mon Nov 24 2025

Breezy conditions expected at all terminals during the 12Z TAF
period. VFR conditions prevail through much of the period. A strong
cold front will move through late in the period, increasing winds
and swapping wind directions to the northwest. This will be the
primary aviation concern for the 12Z TAF period.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...High Wind Warning from noon today to midnight MST tonight for
     WYZ106.
     High Wind Warning from 8 AM this morning to 5 AM MST Tuesday
     for WYZ110.
     High Wind Warning from noon today to 5 AM MST Tuesday for
     WYZ116-117.
NE...High Wind Watch from this evening through Tuesday afternoon
     for NEZ002-003-095-096.

&&

$$

SHORT TERM...AM
LONG TERM...MM
AVIATION...AM