428
FXUS65 KCYS 292112
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
312 PM MDT Fri Aug 29 2025

.KEY MESSAGES...

- Scattered precipitation chances continue for Friday and
  Saturday, though drier conditions are expected to return
  Sunday onwards.

- Warming trend starts Sunday, with fire weather concerns slowly
  creeping up to start the work week.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 309 PM MDT Fri Aug 29 2025

An upper-level shortwave moving across the Colorado/Wyoming border
this evening will bring yet another round of precipitation to the
CWA. Current visible satellite shows mid-level clouds beginning to
float into the western portion of the forecast area. Given the lack
of instability across Wyoming, thunderstorms are not expected this
afternoon. Hi-Res guidance shows more stratiform-like precipitation
moving in from the southwest early this evening. Embedded pockets of
CAPE could certainly spark some rumbles of thunder, however, it is
not expected to be widespread across southeast Wyoming.
Precipitation will arrive in the Nebraska panhandle later this
evening as the shortwave gradually moves eastward. CAPE values
overnight in the panhandle will actually be higher than during
the day as the shortwave moves through. CAPE values will be high
enough for a few thunderstorms to develop overnight. Severe
storms are unlikely, but heavy rain can be expected with
elevated PWATs. Scattered showers will persist across much of
the CWA overnight and continue into Saturday morning.

Storms will get an earlier start on Saturday as some lingering
energy from the shortwave hangs around. Storms could start as early
as late morning as CAPE values increase throughout the day,
maxing out at around 1000 J/kg of MUCAPE during the afternoon.
Once again, given the environment, severe storms are not likely,
however, cannot rule out a few strong storms with gusty winds
and small hail. Storms will diminish during the evening hours as
the upper-level shortwave continues to push eastward into
central Nebraska, ushering in drier air behind it.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 309 PM MDT Fri Aug 29 2025

The persistent wet pattern will come to an end Sunday after about 10
days of cool temperatures and high dewpoints across the area. On the
synoptic scale, the slow moving and disorganized upper level low
responsible for unsettled weather today and tomorrow will be on the
way out Sunday, leaving light northerly flow over the area. Despite
ridging trying to build back into the western CONUS, temperatures
will remain pleasantly cool, about 5F below seasonal averages for
our area. Afternoon convection looks very limited, thanks to dry air
spilling over the area in northwest flow. Expect a similar story on
Monday and Tuesday with temperatures slightly warmer on Monday and
then steady or a touch cooler on Tuesday. Precipitable water will
remain slightly below average for this period, keeping the
precipitation potential to a minimum.

Model guidance diverges somewhat for Wednesday onward. There is good
agreement that an unseasonably strong upper level low will dive into
the central and eastern CONUS around the middle of the week, but
there is a bit of a discrepancy between ensemble systems in how far
west the edge of the cool airmass will end up. The ECMWF ensemble is
strongly clustered on a more westward position of the trough, which
would bring a noticeable hint of fall into the area for Wednesday
and Thursday. The GEFS system is mostly clustered on a more eastward
position of the trough, which would keep temperatures generally near
seasonal average through the middle of the week ahead. However, both
scenarios bring some limited chances for rainfall back into the
forecast, just from entirely different mechanisms. The westward
solution may allow for some stratiform rainfall due to modest
shortwaves rotating around the flank of the broad upper level low.
The eastward solution would allow for some limited monsoon moisture
to return to the area by Thursday or Friday, coming more in the form
of afternoon convective activity.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1155 AM MDT Fri Aug 29 2025

Scattered showers and storms will be the main concern for the TAF
period. This afternoon, showers and storms will develop across
Wyoming. Storms could reduce visibility and lower CIGs below VFR
criteria. Storms will move into the Nebraska panhandle tonight, with
showers lingering across Wyoming. Low CIGs will start to creep back
into portions of the Nebraska panhandle tonight and tomorrow
morning.

&&

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

&&

$$

SHORT TERM...SF
LONG TERM...MN
AVIATION...SF