889
FXUS65 KRIW 140003
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
603 PM MDT Mon Jul 13 2026

.KEY MESSAGES...

- The Extreme Heat Warning continues through 9 PM Tuesday, as
  daytime high temperatures run 10 to 15 degrees above normal.

- Isolated showers and thunderstorms, mainly over the Absaroka,
  Gros Ventre, and Wyoming Ranges, continue until around sunset
  Monday. The primary hazard from these showers and storms will
  be gusty outflow wind 35 to 45 mph.

- Temperatures trend slowly downward beginning Wednesday through
  the end of the week, with shower and thunderstorm chances
  slowly increasing.

&&

.UPDATE...
Issued at 1226 PM MDT Mon Jul 13 2026

No notable changes with this update. Temperatures remain hot today,
with most lower elevation locations seeing highs 95 to 105 degrees.
Still, with the high pressure system shifting slightly east,
enough moisture will be around to get some clouds over the area,
mainly the western mountains. A few could be virga or light
showers. Gusty outflow winds are the main hazard with any of
these.

&&

.DISCUSSION...
Issued at 350 AM MDT Mon Jul 13 2026

A day after several all-time record highs were broken, today will
not bring much relief. The center of the dominating high pressure
system has now shifted farther east. This will allow slightly cooler
air to work its way south into Wyoming today, already noted with a
northerly breeze across the northern Bighorn Basin early this
morning. While this will bring highs down by 5 to 10 degrees across
northern Wyoming...that still puts nearly all lower elevations in
the 95 to 105 degree range today. Elevated moisture will increase
slightly, leading to more cumulus clouds and virga, especially
across the western half of the state. With large temp/dewpoint
depressions at the surface (60-70 degrees), virga will carry a
strong but isolated wind threat this afternoon. The lack of a more
widespread breeze will be the limiting factor on fire weather
conditions today; while humidity will drop into the single digits
for much of the area, generally lighter wind precludes the issuance
of any fire weather hazards.

Tuesday will bring very similar conditions, with temperatures again
peaking in the 95 to 105 degree range, perhaps slightly higher again
across the Bighorn Basin as heights rise subtly. Convection coverage
will ramp up a little further as moisture increases, again mostly of
the virga form. The hot temperatures will remain the primary weather
impact; the Extreme Heat Warning will continue through sunset
Tuesday.

The ridge is expected to shift farther east on Wednesday. This
should allow for increasing monsoonal moisture advection and an
uptick in convection, especially as shortwaves progress through the
flow over the area. Temperatures will decrease in response, though
only marginally - high are still expected to be in the 90s to low
100s across the lower elevations. Moisture advection will be further
amplified on Thursday and Friday as PWAT values approach one inch.
Accordingly, rain chances will increase across the area beginning
Wednesday, with Thursday appearing most favorable for widespread
shower and thunderstorm coverage at the moment.

Ensemble cluster guidance continues to favor anomalously high 500mb
heights through the weekend. While this would not bring any big
pattern changes, additional smaller disturbances and continued
monsoonal moisture is likely to lead to more rain chances across the
area.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 430 PM MDT Mon Jul 13 2026

VFR conditions expected throughout the period at all TAF sites with
dry conditions throughout. Light winds 10kt overnight into
Tuesday morning. Winds increase to around 10kt for most
locations by 18- 20Z, with gusts up to 18kt for KCPR/KRIW/KRKS
due to stronger mixing to the surface. Scattered showers and
thunderstorms will be possible again over the western mountains
Tuesday afternoon. Confidence remains too low to include into
the forecast for KBPI, KPNA, KJAC and KCOD. A few to scattered
passing high clouds overnight with mainly clear skies by 18Z
Tuesday. Otherwise, no other weather elements are expected at
this time.

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...
Extreme Heat Warning until 9 PM MDT Tuesday for WYZ003>006-010-
011-013-016>020-023-025>030.

&&

$$

UPDATE...Wittmann
DISCUSSION...Myers
AVIATION...LaVoie/Lowe