904
FXUS65 KRIW 281836
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1236 PM MDT Tue Jul 28 2026

.KEY MESSAGES...

- Warmer temperatures today, with highs reaching the mid-to-
  upper 80s west of the Divide and mid-to-upper 90s east of the
  Divide.

- Lingering moisture brings isolated shower activity this
  afternoon, focused on southern WY.

- Increasing moisture Wednesday brings widespread showers and
  thunderstorms. Monsoon moisture gets pushed out of the state for
  the end of this week, bringing warmer temperatures and ending
  rain chances.

&&

.UPDATE...
Issued at 1232 PM MDT Tue Jul 28 2026

With less cloud cover today, warmer temperatures will be in place,
with highs in the upper-80s to upper-90s across the area. The latest
hi-res models have isolated showers and storms mainly across western
and southwestern Wyoming this afternoon. Outflow gusts to around 40
mph would be the most likely outcome from any shower or storm. Smoke
from the west is also around today, mainly across northern Wyoming,
but some will be across the whole state. Conditions improve some for
Wednesday, with smoke then increasing over northwest Wyoming
Wednesday night.

&&

.DISCUSSION...
Issued at 241 AM MDT Tue Jul 28 2026

The active monsoon pattern of the past couple weeks that has
brought beneficial rainfall looks to be finally shifting the
rest of the week. The H5 ridge placement centered on the Four
Corners has been efficient in drawing moisture northward, and
will continue today to trigger some shower activity for WY.
Today, the focus of moisture looks to be more across southern
WY, where the best chances for precipitation are setting up this
afternoon. Some brief drying is noted across northern WY today,
so shower activity will be more limited, and focused on higher
elevations. The lower moisture for most of the state will bring
decreased cloud cover, allowing temperatures to jump back well
above normal. Areas east of the Divide will jump into the mid to
upper 90s, while southern WY, with the better shower chances and
cloud cover in the afternoon, will still reach the mid to upper
80s.

A final push of deeper monsoon moisture surges northward
tonight, along with another shortwave wrapping around the ridge.
This will bring much better chances for numerous showers and
thunderstorms for the day Wednesday. Rainfall amounts will be
beneficial again, but storm motions will be high enough to
preclude most flooding concerns during the afternoon.

Once this shortwave sweeps northeast Wednesday night, the H5
ridge bulges to the west, effectively shutting the door on the
monsoon flow, and instead drawing much drier air from the Great
Basin into the state. This will effectively shut down rain
chances for the rest of the week into the upcoming weekend. The
ridge also bulges back to the north, bringing increasing
temperatures across the state. Probabilities for 100 degree
temperatures this weekend currently sit at >60% east of the
Divide, and around 30% west of the Divide, including the greater
Jackson region.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1117 AM MDT Tue Jul 28 2026

Low stratus that had impacted KJAC earlier this morning has
mostly dissipated. VFR conditions are expected to prevail across
all terminals through the TAF period. Showers and thunderstorms
are expected to begin developing shortly after the start of the
TAF period. PROB30 groups are in place at KJAC, KPNA, KBPI,
KRKS, and KCOD due to chances for showers and thunderstorms
between 20Z and about 00Z Wednesday. If any storms move directly
overhead brief MVFR conditions may be possible. Otherwise, the
main concerns will be nearby lightning and gusty outflow winds
of 30-40 mph. A light breeze is expected this afternoon across
nearly all terminals with winds around 10 to 15 mph. These winds
weaken overnight before gradually returning near the end of the
TAF period. Another round of showers and thunderstorms is
expected Wednesday with coverage likely increasing with most
terminals having a chance for a shower or thunderstorm. Mountain
obscuration may be possible at times mainly in association with
any developing convection this afternoon/evening.

Please see the Aviation Weather Center and/or CWSU ZLC and ZDV
for the latest information on smoke, icing, and turbulence
forecasts.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Air Quality Alert until 1 PM MDT this afternoon for WYZ010.

&&

$$

UPDATE...Wittmann
DISCUSSION...Straub
AVIATION...Dziewaltowski