286
FXUS65 KCYS 241750
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1150 AM MDT Sat May 24 2025

.KEY MESSAGES...

- Marginal Risk (Level 1 of 5) for portions of southeast Wyoming
  and western Nebraska on Saturday. Hail and wind are the
  primary threats.

- Unsettled weather expected to continue this weekend through
  next week with daily chances for showers and thunderstorms.
  Temperatures will be near or slightly below average for late
  May.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 1130 AM MDT Fri May 23 2025

Low stratus is currently clearing out of the CWA after ample
moisture advection overnight. Observations from across the area show
dewpoints in the 50s across the Nebraska panhandle, 40s along the
Interstate 25 corridor, and 20s on the west side of the dryline that
is sitting over the Laramie Range. Models like the RAP show
dewpoints continuing to increase in the southern panhandle this
afternoon as southeasterly flow intensifies moisture advection from
the Gulf. A weak disturbance moving overhead will likely spark
convection along the dryline early this afternoon. Storms will push
eastward into Nebraska through the afternoon hours, moving into an
environment more favorable for severe storms.

Model soundings from across western Nebraska are rather aggressive
this afternoon. GFS soundings around Sidney show MUCAPE values in
excess of 2000 J/kg. Effective shear is greater than 40 kts with
steep mid-level lapse rates. These variables lend itself to a
significant hail threat, with hail larger than 2 inches in
diameter possible. Cannot rule out an isolated tornado as well
with effective shear values as high as they are with MLCAPE
values greater than 1500 J/kg. Most Hi-Res guidance also
suggests discrete cells this afternoon which also lends itself
to more of a large hail and isolated tornado threat. Cannot rule
out damaging wind gusts as well with DCAPE values greater than
900 J/kg with storm clusters possible. Most guidance shows a
relatively short window for convection this afternoon.
Initiation will likely be early this afternoon, with peak
intensity of storms expected late this afternoon. Severe storms
will push out of the CWA this evening, with a few lingering
storms possible overnight.

Weak moisture advection will continue overnight, leading to areas of
fog and low stratus Saturday morning, mainly east of the Laramie
Range. Moist southerly flow will continue throughout most of the day
in the mid-levels ahead of an approaching shortwave. This will
increase PWATs into the 90th percentile for NAEFS climatology.
Combined with the vorticity maxes aloft, widespread precipitation
will likely develop during the afternoon. Hi-Res guidance shows most
of the CWA seeing precipitation at some point during the
day/evening. The severe threat will be limited somewhat by a
cooler environment. Model soundings do still show modest
instability, especially around the Cheyenne area, which suggests
this may be where some of the stronger storms are. The clustery
nature of the storms tomorrow will lend itself more to a strong
wind threat, however hail cannot be ruled out. Showers and
storms could linger into the overnight hours, however coverage
of storms will be much lower.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 135 PM MDT Fri May 23 2025

Sunday...Expecting a cool day due to widespread cloud cover and
precipitation coverage, with high temperatures in the 50s east of I-
25, with 60s further west. With a deep, moist airmass in place, low
level upslope east winds and a passing shortwave trough aloft, we
anticipate widespread showers and scattered thunderstorms in the
afternoon and evening.

Monday...Somewhat similar pattern to Sunday, although the flow aloft
turns northwesterly with slightly less moisture available. Still
though, we expect scattered to numerous showers and scattered
thunderstorms in the afternoon and evening.

Tuesday...Northwest flow aloft continues and with adequate low and
mid level moisture, we expect to see scattered late day showers and
thunderstorms, though with less areal coverage compared to Monday.
Warmer temperatures compared to Monday based on 700 mb temperatures.

Wednesday...Another comparable scenario to Tuesday, with north
northwest flow aloft and low level upslope winds, providing enough
shear and instability for scattered afternoon and evening showers
and thunderstorms. Slightly cooler than Tuesday based on 700 mb
temperature trends.

Thursday-Friday...The flow aloft turns northerly, with some drying
noted in the low and mid levels, thus we should see a decrease in
areal coverage of afternoon and evening showers and thunderstorms,
though moisture looks plentiful enough for scattered coverage. With
700 mb temperatures from 7-9 Celsius, maximum temperatures will show
a warming trend.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1145 AM MDT Sat May 24 2025

Very messy TAF forecast as ongoing precipitation alongside new
convection going into the afternoon and low CIGs will make for
difficult forecasting across the region. Areas of thunderstorms
expected this afternoon through this evening with widespread
coverage of precipitation possible through tonight. All TAF
sites have a chance of thunderstorms, with Wyoming terminals
having the best cloud decks outside of KCYS. Otherwise KCYS and
all Nebraska terminals with continue to see mid to low ceilings
through the overnight creating IFR to LIFR conditions. Some
storms could be strong to possibly severe as well, with
localized enhancements to winds and hail possible. Overall wind
field otherwise should be manageable, with winds 10-20 knots
outside of any nearby thunderstorms.

&&

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

&&

$$

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