-- Discussion containing changed information from previous version are highlighted. --
334
FXUS65 KCYS 242357
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
557 PM MDT Tue Jun 24 2025

.KEY MESSAGES...

- Strong to severe storms possible Tuesday and Wednesday
  afternoon. Large hail and damaging winds will be the primary
  concerns.

- Warmer and drier weather expected for the end of the week.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 1200 PM MDT Tue Jun 24 2025

Current visible satellite imagery late this morning shows a thick
layer of low stratus along the Laramie Range and areas eastward.
Further westward, ample sunshine is allowing a cumulus field to
develop, which will likely be the place where storms first fire off
this afternoon. Southeast flow has allowed for ample moisture
advection into the High Plains this morning. Dewpoints in the
50s and 60s will be favorable for storm development, assuming
the low stratus can burn off. Model soundings show plenty of
elevated instability, however a strong capping inversion could
limit storms this afternoon. Models like the GFS and RAP show a
capped environment through the afternoon, eroding by this
evening. Most CAMs, like the NAMNest, MPAS, and newer runs of
the HRRR have really toned down the convection this afternoon,
likely due to the strong cap. The RRFS is the most aggressive
CAM, showing quite a bit of convection through the afternoon and
evening hours. Clearing is happening just south of the Wyoming
border in northern Colorado. If clearing can start encroaching
into the Interstate 25 corridor, it is possible that storms
could initiate. Any storm that can develop and persist, will
have the potential to become severe. MUCAPE values range
anywhere from 1200 to 1800 J/kg with 35 to 45 kts of effective
shear. Elevated pockets of 1000 J/kg of MLCAPE and 800 J/kg of
DCAPE also exist east of the Laramie Range. This will lead to
all hazards of severe weather possible, with the most likely
threats being hail and wind. Heavy rain can also be expected in
storms with PWATs above the 90th percentile for climatology.
This may also lead to flash flooding in isolated areas. Any
storms that do develop will likely push east out of the area by
9 PM tonight.

Another round of storms will be possible Wednesday afternoon as
a weak shortwave moves into the CWA. The shortwave will provide
the forcing to initiate storms, with residual moisture from
today helping to fuel them. Model soundings show less in the way
of instability on Wednesday, but with decent shear. Hi-Res
guidance shows widely scattered storms across the area, with
perhaps a few isolated strong to severe storms possible. Once
again, most of the storm activity will be done by about 9 PM.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 315 PM MDT Mon Jun 23 2025

Thursday and Friday will serve more as transition days in the long
term pattern as southwesterly to westerly flow returns aloft behind
the departing trough. As a result, subsidence will be present aloft
across the CWA on Thursday as the upper-level trough leaves the area
and anticyclonic vorticity advection develops behind the trough. As a
result, dry conditions are expected Thursday and Friday as 700mb
temperatures warm back into the 13 to 16C range. Surface
temperatures will increase back into the 80s and 90s once more, with
Friday being the warmest day across the region. Expecting little to
no precipitation chances with fairly calm winds near the surface
ahead of the next approaching system for Saturday and Sunday.

Saturday will feature an upper-level shortwave pushing overhead,
which will lead to enough forcing to get afternoon showers and
storms once again. Multiple 500mb vorticity lobes will once again
eject out ahead of the approaching shortwave, leading to additional
synoptic lift from CVA across much of the eastern portions of the
CWA. These lobes will force convective initiation Saturday
afternoon. 700mb temperatures remain in the 15 to 17C range, leading
to surface temperatures in the 80s and 90s once again for Saturday.
Additionally another cold front with pass through the region,
initiating showers and storms along and ahead of the front, leading
to afternoon showers and storms. Messy flow develops once more for
Sunday with 700mb temperatures cooling slightly and afternoon shower
and thunderstorm chances remaining for much of the region.
Temperatures on Sunday will drop back into the 70s and 80s behind
the cold front passing through on Saturday.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
-- Changed Discussion --
Issued at 553 PM MDT Tue Jun 24 2025

Cloud cover today has reduced the thunderstorm threat this
evening, but isolated to scattered storms are still possible.
KSNY will see some rain and thunder with gusty winds possible
over the next few hours. This may reach KAIA and KCDR later, but
confidence is lower.

Storms will clear out around midnight, after which time fog and
low clouds will creep back into the High Plains. IFR is likely
at KCYS and KSNY, with MVFR favored at KBFF, KAIA, and KCDR.
This will slowly break again Wednesday morning as winds shift to
north/northeasterly. Another round of fairly widespread showers
and thunderstorms is possible Wednesday afternoon and evening.
-- End Changed Discussion --

&&

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

&&

$$

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