757
FXUS65 KRIW 251013
AFDRIW

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

.KEY MESSAGES...

- Another round of thunderstorms this afternoon and evening,
  mainly over the Wind Corridor (from Rock Springs to Casper),
  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 a few hours ago, including one with a 3 body
scatter spike. Most remained over unpopulated areas though. And
now, things are mainly quiet with 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 be a stray
shower or thunderstorm, mainly across 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 dewpoints 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
and near the mountains in this pattern.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 412 AM MDT Wed Jun 25 2025

MVFR ceilings will remain in place at KCPR through 14Z/15Z, with
a 30% chance for these conditions to drop to LIFR. Have left
this as a SCT group for now. Otherwise, most of the area is
under SKC skies with a streak of mid level clouds from far
southwestern portions to KGEY.

Lingering low-level moisture will allow for more scattered showers
and thunderstorms this afternoon, mainly from KRKS up to KCPR
and eastward. At these terminals, PROB30 groups cover the
possibility of convection during the afternoon. There is a very
low chance (10-15%) of an isolated shower or storm at KBPI,
KPNA, KLND, and KRIW. This weather system finally exits the
area after 03Z, taking the low-level moisture with it. There
will be a bit of wind (10-20 knots) at KRKS and KCPR this
afternoon, otherwise wind will remain below 10 knots through the
TAF period. Skies will clear out once again after 06Z.

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...LaVoie/Rowe