379
FXUS65 KRIW 081000
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
400 AM MDT Sat Aug 8 2026

.KEY MESSAGES...

- Another hot weekend is on tap with many lower elevations
  seeing highs in the 90s with some locations reaching 100
  degrees.

- The combination of hot temperatures, humidity falling below 15
  percent and breezy afternoons will bring elevated to critical
  fire weather both Saturday and Sunday afternoons.

- Hot temperatures continue through Tuesday. Following that, we
  may enter a cooler and somewhat wetter pattern, although
  details of the wettest day and placement of the heaviest rain
  remain highly uncertain.

&&

.DISCUSSION...
Issued at 110 AM MDT Sat Aug 8 2026

One of the big things that meteorologists look for in forecasting is
patterns. And we have had a pattern over most of the past 5 weeks.
And that is that the hottest temperatures occurred on weekends. And
this one looks to be no exception, although maybe by only a few
degrees.

The hottest temperatures will likely be today. Model guidance
continues to show 700 millibar temperatures climbing over 20 degrees
celsius. And this translates to some portions of the area likely
climbing to over 100 degrees this afternoon. Most locations under
5400 feet have at least a 1 in 2 chance of reaching 100 this
afternoon, including the Wind River Basin, the eastern Big Horn
Basin as well as near Casper. Helping to increase the temperature
will be a downsloping southwesterly breeze. And this, combined with
the hot temperatures and humidity falling into the single digits,
will bring the likelihood of critical fire weather. We currently
have a Red Flag Warning in effect for entire area where fuels are
critical. Wind is marginally in some of the northern zones of the
area. However, with the very dry fuels and low humidity, we will let
it go for now. And, it still looks to be a dry day. Mid level
moisture will increase a bit in southwestern Wyoming, and may be
just enough for a few virga showers to develop. The chance is only
around 10 percent at any given spot and with that we left the POPs
largely silent. And, like the past few days, we will have areas
of smoke around that will bring unhealthy air quality at times.

The operative word for Sunday will be slightly, as in conditions
should change, but only slightly. As for the heat, slightly cooler
700 millibar temperatures (about a degree celsius), should also for
slightly cooler temperatures, but only a couple of degrees. And,
relative humidity will be slightly higher. However, only by a few
percent and low enough when combined with the continuing breezy
conditions, will likely bring more critical fire weather in the
afternoon. And finally, with slightly more instability and slightly
more mid level moisture, the chance of a shower or even
thunderstorms will go up slightly in southern and western Wyoming.
The chance is still at most 1 out of 6 and any shower or storm would
likely only bring wind gusts and not any needed rain. And, smoke
may be slightly better, but air quality will likely remain
unhealthy.

As for next week, it looks like a transition week. Monday and
Tuesday still look like rather hot days, with most areas East of the
Divide seeing high temperatures in the 90s. A bit more monsoonal
moisture may try to work in and bring a few showers and
thunderstorms. However, on this day, most would be confined to
western Wyoming and still fairly sparse, with generally a less than
1 out of 4 chance. The ridge should then weaken and move to the
south and east, bring a more zonal flow. This could allow for more
moisture to reach the area and bring an increased chance of
convection. There is still a lot of disagreement in guidance with
details, so determining a more active day or placement of the most
numerous storms is still very difficult at this time. And,
temperatures should trend down starting on Wednesday and especially
for Thursday and into next weekend when a cold front may pass and
bring in some below normal temperatures for the end of next week and
into next weekend. However, until we reach that, it looks like more
of the same for the next four days. That is hot temperatures,
elevated to critical fire weather and little to no chance of
meaningful rain.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 400 AM MDT Sat Aug 8 2026

Largely VFR conditions should continue through 12Z Sunday. The main
possibly impact would be areas of smoke continuing to drift in from
fires to the west. It could bring local MVFR visibility, but we left
this out of the TAFs with the continued difficulty of timing and
placement of the thicker smoke. A gusty breeze will develop this
afternoon, with gusts of 15 to 25 knots possibly at all terminals
between around 19Z and 02Z, with wind decreasing after sunset. In
vicinity of KBPI, KPNA and KRKS, a virga shower with wind gusts past
35 knots can;t be ruled out between 20Z and 03Z. However, with the
chance only around 10 percent, it was left out of the forecast for
now.

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

&&

.FIRE WEATHER...
Issued at 110 AM MDT Sat Aug 8 2026

A combination of hot temperatures, reaching around 100 in some
locations, relative humidity falling into the single digits at
times and gusty breezes will bring elevated to critical fire
weather to all of western and central Wyoming. The strongest
wind will be found across southern Wyoming, and the lightest in
northern Wyoming. Relative humidity recovery will be remain poor
Saturday night, remaining below 40 percent for most locations. s
a result, Red Flag Warning is in effect through Sunday evening
for all locations with critical fuels.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Air Quality Alert until noon MDT Monday for WYZ001>020-022>030.

Red Flag Warning from 11 AM this morning to 9 PM MDT Sunday
for WYZ140-275>283-285>289-300.

&&

$$

DISCUSSION...Hattings
AVIATION...Hattings
FIRE WEATHER...Hattings