711
FXUS65 KRIW 251107
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
507 AM MDT Tue Aug 25 2026

.KEY MESSAGES...

- Shower and thunderstorm chances (30%-70%) exist between 12PM
  and 9PM along and east of the Continental Divide today, with
  the greatest coverage across the northwest Wyoming.
  Thunderstorms will be capable of gusty outflows up to 45 mph
  and lightning.

- Shower and thunderstorm chances exist each afternoon through
  at least Sunday, with more widespread showers and
  thunderstorms Friday through Sunday.

- High temperatures are forecast to be in the upper 70s to 80s
  each day. A few locations east of the Continental Divide could
  see highs in the 90s Wednesday through Friday.

&&

.DISCUSSION...
Issued at 159 AM MDT Tue Aug 25 2026

Showers and a few embedded thunderstorms across southwest Wyoming
are being supported by a shortwave disturbance early this Tuesday
morning. This shortwave and the associated showers and thunderstorms
will shift east across the Green River Basin and Sweetwater County
and fizzle out by sunrise. This shortwave is rounding an upper level
high that is centered over New Mexico and Texas.

Today, this upper high will build north into the Great Basin, with
it`s ridge axis extending into Idaho, placing Wyoming in west-
northwest flow aloft. An embedded disturbance will traverse across
the state and provide support for showers and thunderstorms this
afternoon and evening. Shower and thunderstorm coverage is forecast
to be less widespread compared to Monday and be largely
orographically and diurnally driven along and east of the
Continental Divide. Available moisture will be greatest across the
aforementioned areas thanks to the west-northwest flow aloft and an
associated boundary dropping into northern and central Wyoming.
Thunderstorms are expected today with lifted indices ranging from
-1C to -3C and BLCAPE values around 500 J/kg; however, height rises
aloft will hinder severe thunderstorm potential. That being said, a
few showers or thunderstorms will be capable of gusty outflows up to
45 mph. Showers and thunderstorms are forecast to develop between
noon and 2PM across the higher terrain along the Continental Divide
and shift east-southeast through the afternoon. Shower and
thunderstorms largely come to an end by 9PM tonight, with a few
light showers possible across northwest Wyoming until 11PM. With
700mb temperatures around 10C, anticipate high temperatures in the
upper 70s and 80s.

The upper level ridge is forecast to begin a slow shift east across
Wyoming early Wednesday and be east of Wyoming by Thursday evening.
The ridge axis is currently forecast to be over western Wyoming on
Wednesday as another weak disturbance propagates around it. Although
there will be some support and available moisture aloft, height
rises will keep shower and thunderstorm activity orographically and
diurnally driven across southwest Wyoming and along and east of the
Continental Divide. On Thursday, the ridge axis shifts east across
Wyoming and places western Wyoming in west-southwest flow by peak
heating. This west-southwest flow will funnel Pacific moisture into
the area and provide support for diurnal shower and thunderstorm
development across west and northwest Wyoming. Because the ridge is
over Wyoming on both Wednesday and Thursday, temperatures are
expected to warm into 80s west of the Divide and mid 80s to mid 90s
east of the Divide both afternoons.

Ensemble guidance is in consensus that the Intermountain West will
be positioned between the ridge in the central CONUS and an
approaching Pacific Northwest trough on Friday. This places Wyoming
in southwest flow with Pacific moisture funneling into the region.
This looks to be the pattern Friday through at least Sunday morning
as the Pacific Northwest trough shifts east. The specific details on
timing, precipitation amounts, and coverage are unknown at this time,
however, confidence in an active weather weekend is increasing.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 507 AM MDT Tue Aug 25 2026

VFR flight conditions are forecast throughout the TAF period.
Scattered showers and thunderstorms are forecast to develop across
the higher terrain of western and central Wyoming after 18Z/19Z and
shift east through the afternoon. There is a 30 percent chance of
showers or thunderstorms at KCOD, KCPR, KRIW, KWRL, KLND, KPNA,
and KBPI between 20Z, at the earliest, and 03Z Wednesday,
respectively. PROB30 groups have been maintained at the
aforementioned terminals due to the scattered nature of
convection and uncertainty in timing and impacts at a terminal.
There is a 10 to 20 percent chance of a shower or thunderstorm
at KJAC and KRKS during the same timeframe, but there is no
mention in TAF at this time given the low chances. Showers or
thunderstorms will be capable of frequent lightning and 35 to 40
kt outflows. Brief instances of MVFR flight conditions cannot
be ruled out if a thunderstorm goes directly over a terminal.
Expect winds to be 12 kts or less throughout the entire TAF
period, with gusts of 18 to 20 kts at KRKS in the afternoon and
at KRIW around sunset.

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

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Gerhardt
AVIATION...Gerhardt