846
FXUS65 KCYS 132128
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
328 PM MDT Wed Aug 13 2025

.KEY MESSAGES...

- Hot temperatures and critical fire weather conditions are
  expected Wednesday and Thursday.

- Isolated to widely scattered PM showers and thunderstorms will
  return for Thursday onward.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 306 PM MDT Wed Aug 13 2025

A surface trough is going to push through Southeast Wyoming this
evening to produce some storms in the Northern half of the forecast
area. Looking at mid level water vapor there is some moisture
dropping southeast through the northern counties of Southeast
Wyoming and the northern portion of the Nebraska panhandle. There is
a vort max that will skirt the South Dakota and Nebraska border
coupled with some weak warm air advection. This area of the Northern
panhandle makes it most favorable for storm development or create
the most favorable environment for thunderstorms. Some of the hi-res
guidance has the trough moving more north into South Dakota while
other guidance keeps this feature along the border. So I kept pops
low to represent this uncertainty. SPC mesoanalysis also has about
500 CAPE with 30 knots of shear. With that low of CAPE it is
unlikely that any thunderstorm tapping into this energy pool will
become severe however a gusty shower cannot be ruled out.

Thursday, An upper level shortwave will be responsible for more of
the scattered showers and thunderstorms in the late afternoon and
evening. Moisture looks to retreat back westward to the Laramie
range in the late morning to early afternoon. As this wave lifts
through our region storm motion looks to follow to the northeast.
CAPE and shear look to remain minimal so severity looks uncertain.
SPC has kept our area in general thunder for tomorrow with a
Marginal risk further east.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 306 PM MDT Wed Aug 13 2025

An upper level ridge pushes off to the east at the start of the
long term with westerly flow aloft becoming southwesterly and
moisture advection pushing in at lower levels for Saturday and
Sunday. This will increase the threat of afternoon thunderstorm
activity as a pulse of energy pushes through along with rain
chances hitting the ground on the aforementioned days primarily
across our northern counties, from Niobrara into Box Butte.
Drier air will hold firm across the western zones limiting any
thunderstorm and precipitation chances. There remains some
uncertainty to how much rain will actually reach the ground due
to the fact that dry air has been in place for a while. This
combined with the thunderstorm activity may bring the chances of
dry lighting, creating some concerns regarding fire weather.
Late Sunday into at least mid-week, the ridge that pushed off to
the east early in the long term will retrograde to the Four-
Corners region, bringing back westerly flow aloft. All the
global ensembles show a ridge building in next week, there is
some disagreement as to the amplification of the ridge and how
warm we will get. This mainly has to do with a low pressure
system moving into the Pacific Northwest which may impact how
amplified the ridge will be over us which will be monitored
going forward.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1123 AM MDT Wed Aug 13 2025

Isolated thunderstorms may impact KCDR and KAIA this afternoon
possibly dropping to MVFR conditions, but coverage will be
around 30 percent or less. Chances of thunderstorms will remain
low, below 10 percent, for most other locations. Relatively
quiet for Aviation concerns across the remainder of the CWA
today into tonight, with generally VFR conditions prevailing.
South winds will become westerly through this afternoon into
tonight.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning until 8 PM MDT this evening for WYZ418>422-
     424-425-427>429.
NE...None.

&&

$$

SHORT TERM...MM
LONG TERM...RZ
AVIATION...RZ