285
FXUS65 KRIW 190636
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1236 AM MDT Wed Aug 19 2026

.KEY MESSAGES...

- Mainly dry and warmer today across the area. Elevated fire
  weather is likely this afternoon is southern Wyoming.

- Rather hot Thursday and Friday with widespread highs in the
  90s. Any thunderstorms would be confined to in and near the
  mountains.

- Deeper monsoonal moisture returns for the weekend and much of
  next week, bringing an increased chance of daily showers and
  thunderstorms.

&&

.DISCUSSION...
Issued at 1230 AM MDT Wed Aug 19 2026

We still have a few showers out there early this morning, but these
should be gone by sunrise. It finally looks like we will get a break
from the monsoon, but it is like a shark. It is only leaving for a
brief interlude, it will be back for more, but there will be
break.

The main concern the next few days looks like it will
shift to more hot temperatures. A ridge across the desert
southwest will slowly build to the north, and bring a gradual
rise in temperatures over the next few days. The rise in
temperatures begins today, with widespread mid to upper 80s
across most of the lower elevations, with a few locations
possibly touching 90. As for precipitation, we can`t completely
rule it out but the chance will be close to zero for 95 percent
of the area. We did add some slight chance POPs across southern
Lincoln and western Sweetwater Counties where just enough
moisture may linger for an isolated shower. With the dry low
levels, it would likely only be virga. But even here, the
chance is only 1 out of 6. Normal to below normal precipitable
water levels should keep the rest of the area rain free. There
is one other concern. There will be a bit of breeze developing
in southern zones, and relative humidity will be falling to
around 15 percent. This raises some concern for fire weather. At
this time, the chance of getting 3 hours of critical fire
weather is less than 1 out of 3, so we will not issue any fire
weather highlights. Elevated fire weather will be likely for a
few hours this afternoon though.

As we head to Thursday and Friday, the main concern will be heat as
700 millibar temperatures approach 20 celsius in portions of the
area. On Thursday. most of the population centers below 6000 feet
will have at least a 1 in 2 chance of high temperatures over 90.
Friday still looks like the hottest day, with locations below 6500
feet having at least a 3 out of 5 chance of high temperatures over
90. Areas below 5000 feet will have a 1 in 2 chance of high
temperatures over 95. The good news is this will be Wyoming heat,
meaning humidity will remain low, meaning it should not be dangerous
heat. As for potential convection, chances will increase each day as
monsoonal moisture begins to creep back in. However, as per the
usual progression, it will be largely at the mid levels first.
Through Friday, most convection would be confined to the mountains
with nothing more than a 1 out of 3 chance in any particular
spot. And with many of the showers, rain may not even reach the
ground. As for fire weather concerns, wind should remain light
to moderate so critical fire weather is not expected despite the
low humidity.

We will should be back in the monsoonal pattern on Saturday as
deeper moisture spreads back over the area. Precipitable waters have
the potential to climb over 150 percent of normal starting on
Saturday and continuing through much of next week. All areas will
have a chance of showers and storms starting on Saturday. As for the
most impacted areas, the majority of guidance favors the maximum
impact in western Wyoming this weekend, but confidence on this is
low. There will be the usual ebbs and flows in the coverage of
convection into next week, and it is difficult to nail down details
this far out as to what day will be the most active. As for
temperatures, with more cloud cover temperatures should begin to
cool starting Saturday. Overall though, temperatures should remain
largely above average into next week. So after around a three day
break, the monsoonal pattern of diurnal convection likely returns
this weekend.
&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 944 PM MDT Tue Aug 18 2026

VFR conditions are expected through the period as any lingering
convection ends over the next couple of hours. Lighter wind and
decreasing clouds are expected overnight. No terminal impacts are
expected on Wednesday as convection potential is very low. KRKS will
see gusts to 25 knots Wednesday afternoon, with lighter wind
elsewhere.

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 1230 AM MDT Wed Aug 19 2026

A combination of an afternoon breeze and humidity falling to
around 15 percent across portions Unita, Sweetwater, Sublette
and southern Lincoln Counties will bring elevated to near
critical fire weather this afternoon. Although relative humidity
will remain low through Friday, lighter wind should improve fire
concerns somewhat.

&&

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

&&

$$

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