641
FXUS65 KCYS 101119
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
519 AM MDT Sun Aug 10 2025

.KEY MESSAGES...

- Scattered showers and thunderstorms expected through the
  weekend. A few strong to marginally severe storms cannot be
  ruled out with gusty winds and hail.

- Dry weather expected with a warming trend for Monday through
  Wednesday. Slightly cooler for Thursday through Saturday with
  isolated to widely scattered late day showers and
  thunderstorms.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 415 PM MDT Sat Aug 9 2025

A convergence boundary roughly around the Interstate 80 corridor
between Cheyenne and Sidney has produced a round of
thunderstorms earlier this afternoon. Elevated dewpoints in the
50s and MUCAPE values around 1300 J/kg in the southern Nebraska
panhandle fueled several strong storms. CAM guidance like the
HRRR has been inconsistent, not even showing the convection that
happened earlier this afternoon. After finally picking up on
the afternoon storms, it has gotten rid of the evening/nighttime
convection it originally had. Going forward, the rest of the
afternoon will likely be relatively quiet with the atmosphere
having been worked over by the early round of storms. Cannot
rule out an isolated strong storm or two, but environmental
parameters seem marginally severe at this time. Heading into the
evening and overnight hours, some lingering instability will be
present. Combined with an upper-level disturbance moving
through the trough over the center of the country, some
additional storms could be possible again overnight. Luckily,
the environment tonight does not look conducive for severe
storms.

The aforementioned upper-level disturbance will push cooler air
aloft into the CWA. This will lead to below average high
temperatures which will help stabilize the atmosphere. 700 mb
temperatures will fall to the single digits, leading to highs 5
to 10 degrees below average for mid-August. As a result, model
soundings do not show much in the way of instability. Soundings
from the GFS show MUCAPE maxing out around 600 J/kg. DCAPE
values aren`t even that high either. Despite this, CAMs still
show storms developing during the day Sunday. Another shortwave
will swing through the main trough over central CONUS, providing
the lift needed to produce storms. Given the current
parameters, severe storms do not seem likely, however, elevated
dew points in the Nebraska panhandle could produce a few strong
storms with gusty winds and hail.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 415 PM MDT Sat Aug 9 2025

Monday...Some drying noted aloft on northwest flow, so will maintain
a dry forecast for now. High temperatures slightly warmer than
Sunday with 700 mb temperatures near 12 Celsius.

Tuesday...The warming trend continues as heights and thicknesses
increase. 700 mb temperatures near 14 Celsius will yield high
temperatures from the lower 80s to lower 90s. Continued dry with
minimal low and mid level moisture.

Wednesday...With 700 mb temperatures rising to near 18 Celsius,
maximum temperatures will rise to the upper 80s to near 100 degrees.
Continued dry with lack of low and mid level moisture and warm
temperatures aloft.

Thursday...Continued hot as 700 mb temperatures remain about the
same. With a slight influx of low and mid level moisture, and a
passing shortwave trough aloft, we expect to see isolated to widely
scattered afternoon and evening thunderstorms.

Friday...Slightly cooler as 700 mb temperatures drop a little.
Enough low and mid level moisture for isolated to widely scattered
late day showers and thunderstorms.

Saturday...With weak disturbances in the flow aloft, and adequate
low and mid level moisture, we anticipate isolated to widely
scattered afternoon and evening thunderstorms once again. Little
change in high temperatures based on 700 mb temperature trends.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 510 AM MDT Sun Aug 10 2025

Westerly flow aloft will become northwesterly on Sunday as an upper
level trough settles over the northern Front Range. Showers and
thunderstorms are expected to increase in coverage for most of
southeast Wyoming and central/southern Nebraska Panhandle Sunday
afternoon through early Sunday evening. Some fog is still possible
this morning for the eastern plains but chances are looking
rather low.

HAZARDS/WEATHER TRENDS: Some patchy fog and areas of low clouds
may still develop this morning. However, with the lack of
development overnight chances are looking rather slim for any
further development through the remainder of the morning. All
terminals other than KRWL will see showers and thunderstorms
developing in the afternoon hours and possibly linger into the
early evening. Brief MVFR to IFR VIS due to heavy rain and gusty
winds are possible with the activity between 19z Sunday and 00z
Monday. Kept PROB30 groups for these locations for now, but may
need to add prevailing and TEMPO groups for lines of
thunderstorms if model trends continue.

&&

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

&&

$$

SHORT TERM...SF
LONG TERM...RUBIN
AVIATION...SF