874
FXUS65 KCYS 212305
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
505 PM MDT Mon Jul 21 2025

.KEY MESSAGES...

- Expect hot temperatures again today with near critical fire
  weather conditions in Carbon County.

- Widely scattered showers and storms return this
  afternoon/evening and again on Tuesday. A few isolated storms
  may become strong to severe, mainly in the Nebraska
  panhandle.

- There is potential for more widespread showers and
  thunderstorms on Wednesday and Thursday along with a modest
  cool down.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 246 PM MDT Mon Jul 21 2025

A strong ridge of high pressure building over the Gulf Coast has
allowed above average temperatures to persist over the area for the
last few days. Temperatures this afternoon remain quite roasty, with
a few spots in the panhandle already at 100 and in the upper 90s.
Aside form the heat, the location of the ridge has allowed a weak
plume of monsoon moisture to push into the CWA aloft. This has
allowed a few weak echoes to pop up on radar early this afternoon.
Observations across the area, as well as model soundings indicate a
very dry surface. Because of this, it is likely that little, if any
precipitation makes it to the ground this afternoon given relative
humidity under 20 percent across most of the CWA. The main concern
in any showers or storms this afternoon will be rogue severe wind
gusts. Model soundings show a deep inverted-v profile with DCAPE
values well exceeding 1200 J/kg for most of the CWA. Cannot rule out
hail in the panhandle with MUCAPE values around 1200 J/kg, however
effective shear is quite weak. Some Hi-Res guidance has storms
lingering through part of the overnight hours as MUCAPE values
actually increase overnight. Models like the HRRR and RAP show
higher amounts of MUCAPE overnight then during the afternoon today.
As a result, cannot rule out a severe storm or two tonight.

Tuesday looks almost like a carbon copy of today. With the ridge
still in place over the Gulf Coast, above average temperatures will
continue with the plume of moisture aloft. The surface will remain
very dry with model soundings still showing deep inverted-v profiles
across the area. Any showers or storms will have the potential for
severe wind gusts with DCAPE values above 1000 J/kg for most of the
area. Instability and shear continue to lack, however, cannot rule
out another round of nocturnal convection/showers as hinted by
Hi-Res guidance. There looks to be a slight uptick in
instability overnight, though it may not be enough to get any
severe storms. Regardless, will continue to monitor newer model
runs for any changes.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 246 PM MDT Mon Jul 21 2025

Models in good agreement mid to late week showing a typical
monsoon pattern over the southwestern US and most of the Front
Range. NAEFS still showing PWAT above the 90th percentile for
the eastern plains and pushing the 98th percentile for parts of
western Nebraska Wednesday. Slightly lower PWATS on Thursday,
but still above the 90th percentile in areas over far eastern
Wyoming and western Nebraska. With all models showing shortwave
energy moving overhead both days, and ample low level convergence
along the mountains as surface winds shift into the east across
the high valleys and eastern plains, kept POP near 60 percent
with scattered to possibly numerous thunderstorms both days.
This is a favorable pattern for heavy rainfall and lines of
thunderstorms training over the same area. WPC keeps the
Marginal Risk for excessive rainfall over our area and wouldn`t
be surprised to see a Slight Risk in future updates. Can`t rule
out some strong to severe thunderstorms on Wednesday with 0-6km
shear around 35 knots and CAPE between 1500 to 2500 j/kg in the
afternoon, along and east of the I-25 corridor. Severe weather
threat is expected to lower on Thursday with lower shear values.

As we head towards the weekend, models indicate the upper level
ridge axis restrengthening over the eastern plains, while the
595-598dm upper level high nudges northwards but remains over
Texas and the deep south. With all models showing 700mb
temperatures between 15c and 20c during the weekend, expect a
potential heat wave across the region with highs in the 90s for
most locations, and between 100 to 105 for the hotter lower
elevations. Although thunderstorm chances should be limited due
to increased subsidence/dry air aloft, there is evidence of some
weak disturbances lifting northward out of the subtropics (GFS
and Canadian mostly). These features will likely result in some
brief midlevel monsoon moisture advection, but impacts should be
limited. Kept some mention of thunderstorms, but did not go
higher than 20 percent POP.

Further out, all models show another big monsoon push for the
last few days of July with a return to an active pattern
possible by early August.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 502 PM MDT Mon Jul 21 2025

Primary aviation concern this afternoon and evening will be
isolated to scattered gusty showers and thunderstorms. Sudden
gusts will be possible with any showers or storms that develop
this afternoon. Overnight will be quieter with calm winds and
clearing skies. Winds return tomorrow afternoon along with
another round of showers and storms.

&&

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

&&

$$

SHORT TERM...SF
LONG TERM...TJT
AVIATION...AM