305
FXUS65 KCYS 300548
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1148 PM MDT Tue Jul 29 2025

.KEY MESSAGES...

- A conditional threat for scattered strong to severe
  thunderstorms will be present each afternoon and evening
  through Thursday.

- Confidence in storm development is low, but the primary
  hazards will be strong winds, heavy rainfall, and isolated
  large hail with any storms that manage to develop.

- A warming trend returns for late week along with dryer
  conditions and potential fire weather concerns expected west
  of the Laramie Range.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 230 PM MDT Tue Jul 29 2025

Abundant moisture has returned to the area, at least along and east
of the Laramie Range. GOES water vapor imagery shows a narrow plume
of mid to upper level moisture streaming out of the monsoon region
to the south. Meanwhile, the surface high over the Northern Plains
has backed up against the Laramie range, supporting an unusually
humid day for the High Plains. Widespread 60+F dewpoints are
present along and east of I-25, with some 50+F dewpoints
creeping into the Shirley Basin and northern Carbon County.
While the low clouds have mostly broken up, mid to high level
cloud cover is still keeping temperatures on the cool side in
the High Plains. The capping inversion is thus still in place
east of I-25 and north of I-80. Deeper convection is already
getting going in Carbon/Albany counties where the environment is
uncapped. Expect this to increase in coverage and intensity
over the next several hours and begin to move eastward. There is
still uncertainty for the High Plains. While there was ample
elevated instability earlier this morning, some somewhat
unexpected AM convection has already tapped that, and reduced
MLCAPE along the WY/NE state line. This means we still have
fairly low confidence in how this will play out east of I-25.
After that, we will need to watch for a cluster of thunderstorms
expected to develop over central and northwest Wyoming that may
move into our northern zones during the evening hours. This
looks to enter Converse county around 8PM and clear out of the
northern NE panhandle around 1-2AM. The main hazards today
remain strong winds, heavy rainfall, and isolated large hail.

Once thunderstorm finally clears out late tonight, upslope flow will
kick up again and push another round of low clouds and patchy fog up
against the Laramie Range. This surge of moisture looks even a
little stronger, and should push further into the valleys/basins
west of the Laramie Range too. A strong capping inversion will
emerge once again along and east of the Laramie Range, presenting
the same failure mode and potential uncertainties with convective
potential for Wednesday afternoon and evening. With fairly strong
low-level upslope flow and Hi-Res models showing cooler afternoon
high temperatures, cloud cover may be even stickier tomorrow, but
confidence is still quite low. There will also be another
possibility for a late evening thunderstorm complex to move through
our northern zones.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 230 PM MDT Tue Jul 29 2025

Thursday through Saturday:

A mid to upper ridge will remain prominent from the Four
Corners region into the northern Great Plains as upstream
troughing advances into the Pacific Northwest. This will result
in a gradual drying trend aloft, along with hotter temperatures
and a slight decrease in shower and thunderstorm coverage.
However the first portion of this period looks rather active
with decent chances for a few stronger storms on Thursday. The
combination of low afternoon humidity values and breezy
afternoon winds may lead to enhanced fire weather conditions,
particularly west of the Laramie Range.

Sunday and Monday:

The aforementioned trough will progress through the Great Basin
while causing a gradual erosion of the upper ridge across the
region. A basal wind max should advance towards the area on Sunday
with shortwave perturbations providing additional forcing for ascent
into mid week. Therefore cooler temperatures and increasing shower
and storm coverage appears possible during the early to mid portion
of next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1139 PM MDT Tue Jul 29 2025

Although a low amplitude ridge aloft will exist across the
region, moist upslope flow and monsoonal moisture will help
produce scattered to numerous showers and thunderstorms, mainly
during the afternoon and evening hours.

Wyoming TAFS...For Rawlins, scattered clouds near 10000 feet
will occur.

For Laramie, scattered to broken clouds from 3500 to 8000 feet
will occur, with fog from 10Z to 14Z, reducing visibilities to
3 miles and ceilings to 1500 feet.

For Cheyenne, ceilings will range from 200 to 1500 feet until
19Z, with occasional thunderstorms and fog until 08Z, reducing
visibilities to 3 miles, then ceilings will range from 3500 to
5000 feet after 19Z.

Nebraska TAFS...For Chadron and Alliance, ceilings will range
from 2500 to 8000 feet, with fog from 11Z to 15Z, reducing
visibilities to 3 miles and ceilings to 900 feet.

For Scottsbluff and Sidney, ceilings will range from 2500 to
6000 feet, with occasional thunderstorms at Scottsbluff until
08Z, producing wind gusts to 35 knots, visibilities to 4 miles
and ceilings to 1800 feet, and fog at Sidney from 09Z to 15Z,
reducing visibilities to 3 miles and ceilings to 1500 feet.

&&

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

&&

$$

SHORT TERM...MN
LONG TERM...SPM
AVIATION...RUBIN