749
FXUS65 KRIW 101857
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1257 PM MDT Sun Aug 10 2025

.KEY MESSAGES...

- Slight chances (15%) for showers and isolated thunderstorms in
  Natrona and Johnson County this afternoon.

- Lighter winds and mostly dry conditions over the next 3 to 5
  days with a warming trend through mid-week. Wednesday and
  Thursday look to be the hottest days of the week.

- Fire weather concerns return for Wednesday and Thursday as
  winds increase.

&&

.UPDATE...
Issued at 1255 PM MDT Sun Aug 10 2025

A few showers and isolated thunderstorms continue to persist across
Johnson County this afternoon. These are associated with a shortwave
digging out of MT on the backside of the longwave trough that is now
centered over the northern Plains. Increased PoP coverage across
Johnson County as there is a bit more moisture to work with today
(PWATs around 0.8"), but generally kept as isolated (15% chances) as
model guidance still struggles to resolve any longer duration storms
or showers. There is a slight chance (10%) that these showers and
storms could also initiate off of the southern Bighorns and Casper
Mountain, which would track into Natrona County, so have added some
weak PoPs there as well.

Otherwise, not much change to the forecast as we see the ridge start
to re-establish itself over the coming days and thus, the weather
pattern will remain generally quiet. Elevated fire weather does
continue, but light winds will be the limiting factor through at
Tuesday.

&&

.DISCUSSION...
Issued at 224 AM MDT Sun Aug 10 2025

Things are largely quiet on this 2nd sunday of August. A weak
mid level disturbance is producing a few blips on the radar
across the Wyoming - Montana border but these are producing
only a few sprinkles and should be on by shortly after sunrise.
Otherwise, it looks like a nice day for most with comfortably
warm temperatures and a sunny to partly cloudy sky. The only
exception is across portions of Natrona and Johnson County where
a subtle shortwave and maybe just enough mid level moisture may
bring isolated showers or thunderstorms this afternoon
(generally a 1 out of 6 chance). Most places won`t see one
though. And most importantly, a light to moderate wind across
most of the area so this is the first day in a while we have not
had any fire weather concerns.

No concerns on Monday as ridging will control the weather, bring
dry conditions and light to moderate wind. Temperatures will
warm through, but only to near to slight above normal. On
Tuesday, models have slowed the progression of the next front.
This should lead to lighter wind and as a result; fire weather
looks like less of a concern. A very weak shortwave may brush by
far northwestern Wyoming and could bring an evening shower or
thunderstorm, but the chance only looks like about 1 in 10 at
this time and we kept the forecast dry for now.

Concerns begin to ramp up again on Wednesday as the front moves
closer to the area. This will tighten up the pressure gradient and
turn flow to the southwest. This means stronger wind across portions
of the area, especially the southwestern Wind Corridor from Rock
Springs through Casper. This will also warm temperatures
significantly, the widespread highs in the 90s, possibly the upper
90s, in areas East of the Divide. Humidity will be low enough for
critical fire weather, but wind still looks borderline in some
locations. Enough mid level moisture may return to western Wyoming
for isolated thunderstorms, but the chance is generally less than 1
out of 5 and most locations should not see one. The most concerning
day for fire weather looks to be Thursday as the front and shortwave
approach, bringing the breeziest conditions. Convection may be a bit
more this day, but with the lack of low level moisture coverage
stills looks rather sparse at this time. Somewhat cooler
temperatures should return for Friday and Saturday, but temperatures
will still be near to lightly above average across the area.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1115 AM MDT Sun Aug 10 2025

There will be a few isolated showers and storms this afternoon in
Natrona and Johnson Counties as a weak weather system slides
southeast today. Rain chances remain too low for even a PROB30 at
any terminals today. The best chance is at KCPR (10-20%). Prevailing
conditions will remain VFR and skies will be mostly clear to partly
cloudy through the TAF period. There will not be much wind over the
next 24 hours, with wind 5-10 knots and rogue gusts around 15 knots
possible in the afternoon.

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

&&

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

&&

$$

UPDATE...Hensley
DISCUSSION...Hattings
AVIATION...Rowe