101
FXUS65 KRIW 250854
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
254 AM MDT Wed Jun 25 2025

.KEY MESSAGES...

- Another round of thunderstorms this afternoon and evening,
  some could be strong.

- Warm and mainly dry for Thursday and Friday.

- Gusty wind and low humidity may bring elevated to critical
  fire weather for Friday and Saturday afternoons.

&&

.DISCUSSION...
Issued at 249 AM MDT Wed Jun 25 2025

Most places did not get a thunderstorm yesterday. But we did
have some big ones yesterday, including one this evening with a
3 body scatter spike. Most remained over unpopulated areas
though. And now, things are mainly quiet with and storms moving
into South Dakota.

We will have another round of thunderstorms this afternoon as well,
courtesy of another shortwave moving through the area. We could once
again see a few stronger storms with the shortwave and eastern
portions of the area still under the left front quadrant of a jet
streak and lapse rates, both of the low and mid level variety,
remain between 7 and 8 degrees celsius per kilometer. Parts of
Johnson County are still under a marginal risk as well. Storms
should not be quite as strong as Tuesday though. For one, deep
layer shear is less than yesterday, maxing out at around 40
knots versus the 65 knots we had yesterday. CAPE is also around
30 percent less, generally topping out at around 700 J/Kg.
Lifted indices max out at minus 3 versus the minus 5 we had
yesterday. The main area of concern would be across eastern
Wyoming. However, we could have a few storms with decent sized
hail and strong wind gusts once again. Most guidance puts the
best chance across Johnson and Natrona Counties as well as
Sweetwater County, where the best jet support would be located.
Otherwise, it will be a fairly normal late June day with
temperatures close to seasonal normals and light to moderate
wind.

Things look somewhat quieter for Thursday and Friday as flat ridging
takes control of the weather. There could still a stray shower or
thunderstorm, mainly across the northern Wyoming, but the chance is
less than 1 out of 5 at any given point. Temperatures will warm as
well, rising into the 90s on Friday in the lower elevations East of
the Divide. But this will introduce another concern. With the
ridging being flat and some shortwaves brushing by to the north,
there will be a gusty wind at times, especially on Friday and into
Saturday. With humidity falling into the teens and possibly single
digits, elevated to critical fire weather will become a concern. At
this point, the day of most concern looks to be Friday, when the dew
points will be the lowest.

Things may become more active over the weekend as ridging amplifies
across the Pacific northwest and our flow turns more to the
northwest. This could allow a couple of shortwaves to drop southward
into the area and increase the chance of showers and storms, with
the better chance on Sunday when moisture could be a bit
deeper. The ridging should then build further east for early
next week, and bring above normal temperatures. Most
thunderstorms for this time period would likely be restricted to
in and near the mountains in this pattern.
&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1058 PM MDT Tue Jun 24 2025

A weather system will slowly push east through the area tonight.
This weather system has brought low-level moisture into eastern
portions of the area as well as up into the Wind River Basin. This
has resulted in isolated to widely scattered rain showers and
thunderstorms this past afternoon. Some isolated rain showers and
thunderstorms will linger into tonight, with only a low chance (20-
30%) of impacts at KRIW and even lower at KCPR. Other terminals
should remain dry with prevailing VFR through Wednesday morning.

Lingering low-level moisture will allow for more scattered showers
and storms Wednesday afternoon, mainly from KRKS up to KCPR and
southeast. At these terminals PROB30 groups cover the possibility of
convection Wednesday afternoon. There is a very low chance (10-15%)
of an isolated shower or storm at KBPI, KPNA, KLND, and KRIW
Wednesday afternoon. This weather system finally exits the area
Wednesday night taking the low-level moisture with it. There will be
a bit of wind (10-20 knots) at KRKS and KCPR Wednesday afternoon,
otherwise wind will remain below 10 knots through the TAF period.

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.

&&

$$

DISCUSSION...Hattings
AVIATION...Rowe