797
FXUS65 KRIW 120351
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
951 PM MDT Tue Aug 11 2026

.KEY MESSAGES...

- Wildfire smoke remains present across Wyoming, especially the
  northern portions of the state through at least early
  Wednesday afternoon.

- Rain shower potential increases after midnight tonight and
  becomes more numerous across western and central Wyoming on
  Wednesday. Rain chances (50%-90%) become more widespread on
  Thursday with cooler temperatures and rain chances lingering
  into the weekend.

&&

.UPDATE...
Issued at 119 PM MDT Tue Aug 11 2026

One last day of hot and mostly dry conditions is ongoing before a
cooldown starts tomorrow. Convection will be more limited to
southern Wyoming where modest instability will develop this
afternoon. Outflow wind gusts up to 60 mph remain the primary
concern. Hi-res models are showing increasing coverage of showers
starting this evening as the first disturbance arrives from the
approaching trough. This activity will move from southwestern
Wyoming northeastward overnight, increasing in coverage east of the
Divide through Wednesday morning. Cooler temperatures and widespread
rain chances remain on track Thursday into the weekend.

&&

.DISCUSSION...
Issued at 219 AM MDT Tue Aug 11 2026

Another day of hot and mostly dry conditions and hazy/smoky skies
return today with the Four Corners high still in place. The zonal
flow pattern aloft will continue, keeping conditions dry for most of
the CWA today. Virga showers and dry thunderstorms will be possible
across southern portions, roughly along and south of a Cokeville-to-
Farson-to-Muddy Gap line. Instability remains very weak, so these
will likely stay on the virga side just like what occurred
yesterday. Wind gusts of 50 to 55 mph will be the main threat from
these "Green Blobs". The other concern today will be critical fire
weather conditions. Red Flag Warnings are in effect today between
18Z and 03Z Wednesday (12PM to 9PM) for all the same areas from
yesterday except southern Lincoln County/Uinta County. RH values of
8 to 12% will be widespread east of the Divide and include the
Jackson Valley and portions of Yellowstone. Overall, winds will not
be as strong across the CWA this afternoon but gusts of 25 to 30 mph
will occur in many of these areas. Needless to say, burning of any
kind is highly discouraged today. Today will be the last day of this
latest heat wave with highs in the middle 90s for most areas east of
the Divide and upper 80s/lower 90s west of the Divide.

The pattern will begin to shift Wednesday, as the Four Corners high
weakens and erodes and the flow aloft over the Cowboy State turns
more southwesterly irt an approaching trough. Precipitable water
values will increase through the day as a result, with values
approaching 1". This won`t be as strong as the surge of monsoonal
moisture that occurred a few weeks ago in July, but the threat for
locally heavy rain/localized flash flooding will certainly be in
place. Clouds will increase tonight into Wednesday morning leading
to mostly cloudy skies across the forecast area. Temperatures will
be cooler as a result from increased cloud cover, about 3 to 8
degrees cooler. Showers and thunderstorms will be widely scattered
through the day, with western portions having the best chances
through the afternoon. The HRRR brings an area of showers over the
Wind Corridor (Sweetwater to Natrona County), starting around
sunrise and exiting early in the afternoon. Instability remains
rather weak, likely due to the clouds, so not expecting any major
threats. Wind gusts of 40 to 50 mph and locally heavy rain will be
the most likely.

The trend of cooling temperatures continues into Thursday, with
temperatures dropping into the 70s to near 80 degrees. Thursday also
looks to be the best chance for widespread precipitation, especially
across western portions of the state, as the trough moves over ID.
The cooler and wetter conditions continue Friday, as the trough
exits over the Northern Plains and the southwest flow pattern
continues. This will be due to a strong high over the Deep
South/Gulf Coast and a longwave trough over the West Coast. This
will allow embedded shortwaves to move over the Cowboy State,
generating chances for convection across the area each day from
Friday into the middle of next week. The threat for locally heavy
rain will also continue as the monsoonal moisture stays in place as
a result of this pattern.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 950 PM MDT Tue Aug 11 2026

Smoke is expected to be present across the state, especially in the
area of KCOD and KWRL, through at least sunrise on Wednesday.
However, visibilities are forecast to largely remain above 6SM.
Clouds will continue to filter in overnight ahead of an
approaching weather system. There are two "rounds" of rain
showers forecast this TAF period, with showers having
west/southwest to east/northeast motion. Most terminals have at
least a 30 percent chance of rain showers, and associated breezy
winds, during the Wednesday morning hours prior to 20Z. Another
round is forecast to move into the areas of KJAC, KRKS, KCOD,
KBPI, and KPNA after 20Z/21Z. Most activity is forecast to
diminish by 01Z Thursday. A few rumbles of thunder cannot be
completely ruled out, especially Wednesday afternoon. Although
conditions are expected to remain largely VFR, a heavier rain
shower could cause brief periods of MVFR visibilities and
ceilings in addition to gusty 25 kt to 30 kt winds. Outside of
any shower activity, winds are forecast to remain 12kts or less
at most terminals. Occasional gusts around 20 kts are possible
at KRKS, KCPR, KRIW, and KBPI.

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...
Air Quality Alert until noon MDT Wednesday for WYZ001>011-019.

&&

$$

UPDATE...Myers
DISCUSSION...LaVoie
AVIATION...Gerhardt