490
FXUS65 KRIW 281106
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
506 AM MDT Tue Jul 28 2026

.KEY MESSAGES...

- Ridging continues to hold warmer temperatures in place across
  the state. Decreased cloud cover today will allow highs to
  reach the mid to upper 90s east of the Divide this afternoon.

- Slightly lower moisture in the region will bring more isolated
  shower activity this afternoon, focused more on southern WY.

- A surge of moisture into the state Wednesday will bring
  another day of widespread showers and thunderstorms
  statewide. Riding then builds, pushing monsoon moisture out of
  the region for the remainder of the week, bringing warmer
  temperatures and ending rain chances.

&&

.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 /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 501 AM MDT Tue Jul 28 2026

Main morning forecast issue is fog at KJAC. Moisture got trapped
in the valley overnight, and has been meandering about, bringing
brief vis reductions. Once daytime heating starts in the next
couple hours, this cloud deck should lift and dissipate, with
quickly improving flight conditions.

Showers and thunderstorms will return again this afternoon, but
will be more isolated in nature. Most likely impacts will be at
southern sites (KRKS/KBPI/KPNA/KJAC), where moisture is most
available. As thunderstorms are expected to be isolated and
brief, will stay with PROB30 groupings for the day. Shower
activity will dissipate once daytime heating ceases, but
increasing moisture form the southeast will likely keep
midlevel cloud cover around the region through the night
tonight.

&&

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

&&

$$

DISCUSSION...Straub
AVIATION...Straub