FROM: NWS RIW
AREA: NWS RIW County Warning Area
SENT: 2026-07-28T23:40:00+00:00
Area Forecast Discussion: NWS RIW
000
FXUS65 KRIW 282340
AFDRIW
Area Forecast Discussion
National Weather Service Riverton WY
540 PM MDT Tue Jul 28 2026
.KEY MESSAGES…
– Widely scattered showers and thunderstorms persist across far
western and far southern Wyoming until shortly after sunset
Tuesday. Brief heavy rain and gusty outflow wind are the
primary hazards, with gust potential greatest in the south.
– Moisture increases from the southwest beginning early
Wednesday morning and spreads north through the day. Showers
and thunderstorms becoming widespread as the day progresses.
– The bulk of the monsoon moisture shifts east beginning
Thursday, which decreases rain chances while allowing for
warmer temperatures to return to the region. Readings will
likely reach the 90s and lower 100s Saturday and Sunday.
&&
.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 northwestern 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 /00Z TAFS THROUGH 00Z THURSDAY/…
Issued at 400 PM MDT Tue Jul 28 2026
VFR conditions are expected to prevail across all terminals
through the TAF period. A few showers and thunderstorms will be
ending in the first couple of hours of the TAF period. However,
all terminals are expected to remain dry through the overnight.
Any breezy winds will weaken shortly after sunset with light
winds through the overnight across nearly all terminals. Clouds
will increase from the south-southwest by the predawn hours,
with chances for showers over southern/southwestern portions
late in the morning. PROB30 groups have been added to nearly
all terminals from 17Z Wednesday to the end of the TAF period.
Western locations such as KJAC, KPNA, KBPI, and KRKS are
expected to see convection first with chances spreading to the
remaining terminals after 18Z Wednesday. Otherwise, the main
concerns will be frequent lightning, gusty outflow winds of
35kt, and brief periods of moderate to heavy rainfall. Mountains
may be obscured at times mainly during the afternoon/evening
hours Wednesday in association with developing showers and
thunderstorms.
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…
None.
&&
$$
UPDATE…Wittmann
DISCUSSION…Straub
AVIATION…LaVoie/Dziewaltowski
Alert Expiration: 2026-07-29T07:40:00+00:00
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