376
FXUS65 KCYS 151731
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1131 AM MDT Tue Sep 15 2026

.KEY MESSAGES...

- Temperatures bounce back and forth through the week with
  Tuesday the coolest day, followed by a Wednesday warmup,
  Thursday cool off, and Friday back up above normal again.
  Temperatures over the weekend should be around near normal.

- Daily shower and thunderstorm chances continue through the
  week as well with activity remaining

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 1223 AM MDT Tue Sep 15 2026

Upper level pattern will see troughing moving out of the area
and overall southwesterly to westerly flow taking over, followed
by ridging building in on Wednesday and then a quick and weak
shortwave trough riding the periphery of that feature on
Thursday. At the surface, we`ll be in a post-frontal environment
today, with a warm front lifting up on Wednesday and another
modest cold front passing through on Thursday. Under this
pattern, we`ll see a nice rollercoaster to temperatures as highs
will be at their lowest today with 60`s to only mid 70`s for
the day, but tomorrow`s warm front will then bring us back above
normal in the 70`s to 80`s, followed by another cool off on
Thursday as we drop back into the 70`s and approach closer to
near normal for the day. Meanwhile, flow today should allow for
a few showers and storms to develop across the high terrain of
our western zones mainly in Carbon and Albany Counties, but this
activity will be limited by the modest PWAT values present
alongside meager forcing mostly driven by upslope flow. Into
Wednesday increasing moisture should allow for a bit more
widespread isolated to scattered shower and thunderstorm
development, but once again a lack of favorable severe
ingredients will preclude stronger storm development. Seeing a
little bit of instability in the Nebraska Panhandle by the
evening though, so maybe a storm could become stronger if it
moves into this area but unlikely. And Thursday increasing
moisture plus the quick moving shortwave will present widespread
showers and thunderstorms through the day, but with how quickly
this feature moves across we won`t have the time to develop
stronger ingredients and so once again garden-variety storms are
anticipated. Finally, pressure gradients should allow for a
modestly breezy day today but shouldn`t be nearly as strong as
Monday ones, with winds declining on Wednesday and Thursday.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Issued at 240 PM MDT Mon Sep 14 2026

Ahead of a Pacific upper level low a few embedded shortwave impulses
in the southwesterly flow aloft are anticipated to pass through the
area. The best resolved of these shortwave troughs is anticipated
Thursday and will be attended by an impressive fetch of monsoonal
moisture. Ensemble PWAT values are progged to be near or just
outside of the climate maximum. Widspread 1 to 1.5 inch PWAT values
could lead to proficient rainfall potential. GFS forecast soundings
for some spots in the NE Panhandle feature a near saturated profile
with an impressive depth to the warm cloud layer for this area. The
CAPE values are rather paltry however. At the surface a weak lee
cyclone may develop and move NE over the Panhandle locations. Behind
this cyclone cooler air filters in to drive afternoon temperatures a
few degrees lower than Wednesday. The WPC has a marginal risk of
excessive rainfall over our area. Fog is a possibility in the
morning hours east of I-25.

Friday continues the cloudy and wet trend while the Pacific trough
continues to inch eastward. The fetch of monsoonal moisture
continues with widespread light showers and thunderstorms. The near
surface layer does dry out limiting greater rainfall potential. The
marginal risk of excessive rainfall continues in the latest outlook.

This weekend the trough begins to flatten and decay as it nears our
neck of the woods. Continued shower and storm activity in the
afternoon and evening hours is likely to continue, but by this point
the monsoonal flow could be largely shut off with us on the dry
western side of the trough. Southwesterly flow continues in the
very long term with more embedded shortwave troughs which could
provide a stormy start to the work week.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1131 AM MDT Tue Sep 15 2026

Some low clouds with cloud bases around 4-5 kft are present this
morning under an E/SE upslope flow regime mainly for KSNY, KBFF, and
KCYS. The low-level moisture is expected to mix out shortly after
18Z, with VFR expected to prevail for the remainder of the TAF
period. KLAR and KRWL may have some scattered showers in and around
the terminals later this afternoon into the evening, however
confidence and coverage isn`t high enough to include a TEMPO group,
so opted for VCSH instead. Another round of mid-level clouds is
expected to develop overnight, with cigs well above MVFR criteria.
Winds be primarily remain out of the SE, with peak gusts of 25-35
knots.



&&

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

&&

$$

SHORT TERM...CG
LONG TERM...RV
AVIATION...NB