131
FXUS65 KCYS 080506
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1106 PM MDT Mon Sep 7 2026

.KEY MESSAGES...

- Chances for afternoon and evening thunderstorms continue
  through Monday afternoon. Strong gusty winds and brief heavy
  rainfall are the primary threats.

- A temporary drying trend begins Tuesday and possibly
  continuing through the end of the week.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 1241 PM MDT Mon Sep 7 2026

Another toasty day is expected for primarily the Nebraska Panhandle,
as we remain on the western periphery of a longwave upper-level
ridge centered over the Southern Great Plains. Current surface
observations show an elongated surface low extending from the
Dakotas to Colorado, with an axis of low to mid 50 dewpoints located
primarily east of the Wyoming-Nebraska state line. Visible satellite
imagery at this time shows quite a bit of mid and high-level clouds
streaming from the southwest, which has limited surface heating
mainly along the I-25 corridor. Where there is more clearing and
surface heating throughout the Nebraska Panhandle, surface moisture
has managed to mix out rapidly which is expected to continue as high
temperatures in Western Nebraska are expected to reach the upper 80s
to perhaps 90 degrees today. Have nudged high temperatures upwards
for regions along the I-80 corridor in Nebraska and have trimmed
high temperatures for Cheyenne/I-25 corridor to reflect current
trends.

We are starting to see some cumulus development over the Colorado
Rockies and the Snowy Ranges at the time of this discussion, which
will likely be our region of shower and thunderstorm initiation
today as they continue to move off the higher terrain onto lower
elevations later this afternoon mainly south of a Wheatland to
Alliance line. There is some uncertainty in convective coverage this
afternoon into the evening mainly over Southeastern Wyoming as we
are in an area of -50 to -100 J/Kg of SBCINH thanks to 700 mb
temperatures remaining above the 75th percentile. This is keeping us
capped, especially in the areas where mid and upper-level cloud
cover has delayed surface heating. There is a rigorous shortwave
trough located over Eastern Idaho and Northwestern Wyoming that will
lift off to the north and east this afternoon. However with the bulk
of the forcing located well to our north and west, this likely won`t
be enough to initiate additional development over our area.

High-resolution ensemble guidance suggests that convection
initiating to our south and west over Colorado will sneak into
southern portions of the Nebraska Panhandle by mid afternoon. The
primary hazards with storms today will be strong and gusty winds as
indicated by inverted-v profiles on forecast soundings and DCAPE
values of 500-1000 J/Kg. Underneath a broad fetch of monsoonal
moisture embedded in southwesterly flow aloft, which is evident on
mid-level water vapor imagery, brief heavy rainfall will also be a
threat with the stronger storms today. This is reflected on current
mesoanalysis, indicating PWAT across extreme eastern Wyoming and the
Nebraska Panhandle ranging from 1.0"-1.2", which exceeds the 95th
percentile relative to climatology. Not expecting any hydrological
concerns today as cloud-layer mean winds range from 35-40 knots
underneath the stronger flow aloft, so storms will be moving at a
fast clip. Due to the lack of synoptic-scale forcing and dependency
on differential heating of the higher terrain to initiate showers
and storms, expecting most activity to move to the ENE and out of
our region by mid to late evening.

Expect tomorrow to be even drier and quieter than today as the ridge
begins to flatten, placing us in more westerly flow aloft. This will
decrease the amount of monsoonal moisture over our area, which
should also limit any showers and thunderstorms mainly to the higher
terrain west of the I-25 corridor. Per usual Wyoming fashion, any
high-based showers will be capable of producing gusty winds at the
surface. However coverage is not anticipated to be widespread due to
subsidence beneath the ridge. Can expect high temperatures on
Tuesday to be similar to today, although this will depend on how
quickly we can erode any residual clouds from any lingering
convection this evening. Tomorrow evening a cold front is expected
to push through the area, however no rainfall is expected given the
lack of any moisture. The main change behind the front will be gusty
northerly winds, primarily for locations east of the I-25 corridor
along with cooler temperatures compared to overnight tonight.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Issued at 1241 PM MDT Mon Sep 7 2026

Wednesday will begin in a slightly cooler post-frontal air mass,
with high temperatures 5-10 degrees cooler than the previous day,
mainly low to mid-80s for the Nebraska Panhandle and mid-70s
elsewhere. The ridge continues to elongate through the middle of the
work week, placing our area in primarily zonal flow aloft and
therefore mostly dry conditions. A warming trend is expected on
Thursday and Friday as a secondary ridge begins to build across the
Desert Southwest. Will have to monitor fire weather conditions on
both of these days as ensemble guidance is hinting at gusty westerly
winds of 25-35 knots combined with daytime RH values dipping to 15-
20%.

Heading into the weekend, we start to bring back the fetch of
monsoonal moisture ahead of a shortwave trough digging across the
Pacific Northwest, placing Southeastern Wyoming and Western Nebraska
in WSW flow aloft. With the lack of signal for any substantial
forcing from long-range ensemble guidance, no widespread (and
beneficial) precipitation is expected. However can expect a slight
cooling trend with this next push of moisture and the usual diurnal
pattern of scattered afternoon and evening showers and
thunderstorms.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1106 PM MDT Mon Sep 7 2026

Isolated to scattered showers are slowly moving off to the northeast
tonight. Mid-level clouds will continue behind these storms before
starting to clear up after sunrise. Showers will move around KCYS,
KBFF, KCDR, KSNY, and KAIA for the next few hours, with the best
highest chance of impacts expected at KBFF. Gusty and erratic winds
will be possible in and around these showers tonights, with light
and variable winds returning around 10Z. Gusty winds return for the
mid-morning hours, especially at KLAR and KRWL.

&&

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

&&

$$

SHORT TERM...NB
LONG TERM...NB
AVIATION...AM