249
FXUS65 KCYS 120402
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1002 PM MDT Fri Sep 11 2026

.KEY MESSAGES...

- Cold front will move through Friday night, leading to a cooler
  day on Saturday.

- Storm chances increase on Sunday with the potential for
  severe weather.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 223 PM MDT Fri Sep 11 2026

Dry and windy conditions persist this afternoon ahead of an incoming
cold front. This is fueling Red Flag conditions, mainly for
areas east of the Laramie Range. Increased moisture aloft from a
shortwave that moved across the area last night has lead to
some cumulus fields developing this afternoon. There is some
elevated instability as well as some lift from the approaching
front. This could lead to a few isolated showers and storms
developing later this afternoon and evening. Given the dry
surface, it is likely that not much precipitation will make it
to the ground. Wind and dry lightning will be the main concern
in any storms that do develop today. The cold front will move
through later this evening, putting an end to the Red Flag
conditions and shower chances.

A pleasant Saturday is expected for most of the forecast area.
Temperatures will be much cooler behind the front, with highs in the
upper 70s to low 80s. There is another chance for isolated showers
and thunderstorms from another weak shortwave, however there will be
very little instability and shear in the post-frontal
environment. Therefore severe and long lived storms are
unlikely. Sunday looks more promising for storms and severe
weather. A stronger trough will begin to push into Wyoming,
raising temperatures and advecting moisture into the CWA.
Instability will be much higher, with CAPE values rising well
above 1500 J/kg. Ample shear and even high SRH values in the
Nebraska panhandle make severe weather seemingly likely on
Sunday. However, model soundings do show a strong capping
inversion for much of the day which could affect severe weather
potential. Will continue to monitor the storm threat for Sunday
over the next few model cycles.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 223 PM MDT Fri Sep 11 2026

Sunday night into Monday morning shows a cold
front passing over the CWA. After this front moves out, a ridge
starts to build, bringing cooler temperatures and dryer air. Some
storm and shower activity is possible Tuesday evening with return
flow. A shortwave passes through on Thursday evening, allowing the
ridge to continue to build. On Friday the ridge gets pushed out by a
trough forming over the region. Some models are showing
precipitation potential Friday afternoon, but more to come on that
as we get closer. 700mb temperatures are in the 10-15C range in this
long term period. Temperatures start to cool off and feel more like
fall as the week progresses.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1001 PM
MDT Fri Sep 11 2026

A weak cold front has pushed through the area this evening, shifting
surface winds from westerly to either northerly or northeasterly.
There are low probabilities (<15%) of KCYS and the Nebraska
terminals seeing low cloud development, primarily from 09Z to
sunrise given the NE upslope flow. Confidence isn`t high enough
given current obs/trends to include a PROB30 group for MVFR cigs.
Winds will shift to more out of the SE tomorrow at 10-15 knots east
of the Laramie Range. KLAR and KRWL will maintain westerly flow with
gusts as high as 30 knots.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.

&&

$$

SHORT TERM...SF
LONG TERM...ML
AVIATION...NB