509
FXUS65 KRIW 052237
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
437 PM MDT Fri Jun 5 2026

.KEY MESSAGES...

- Elevated to critical fire weather through the weekend, with
  gusty winds (25 to 45 mph) and low humidity (around and less
  than 10 percent).

- Warm today and Saturday, with peak heat occurring Saturday.
  Highs today in the 80s to low-90s, with highs Saturday in the
  mid-80s to near 100 degrees.

- The overall trend next week looks to be windy, with
  temperatures closer to seasonal (70s to low-80s). There are
  also chances for showers and thunderstorms.

&&

.UPDATE...
Issued at 1240 PM MDT Fri Jun 5 2026

Looking at current satellite imagery, you`d be hard-pressed to find
a cloud over the area as dry southwest flow persists. Though a few
clouds will develop through the afternoon, the area remains dry
today, with high temperatures still forecasted in the 80s to
low 90s. The main weather story for today is elevated to near-
critical fire weather, as widespread gusty winds of 20 to 35 mph
occur, in conjunction with humidity values around and less than
10 percent.

&&

.DISCUSSION...
Issued at 224 AM MDT Fri Jun 5 2026

The trough that has been lingering in the vicinity the past
couple days is finally moving to the east, which will open the
door for the next system to impact the NW Rockies. This system
is just starting to drop down the West Coast, and will gradually
buckle a ridge ahead of it across the Rockies during the next
48 hours. Today will start with flat ridging, with nearly clear
skies and temperatures in the 70s and 80s. West winds will be
lighter than yesterday, but a few gusts near 20 mph are possible
across the usual areas of central WY.

The ridge then starts to build in the vicinity tonight into
Saturday, with increasing temperatures aloft. Still noting H7
temps of 16 to 19C, which translates to mid to upper 80s west of
the Divide and into the 90s to the east. There remains an
outside chance of triple digit readings, mainly on the open
ranges of Johnson County and the lowest elevations of the
Bighorn Basin. The placement of the ridge is centered on the
Central Plains, so a weak impulse may nudge into the NW WY Parks
during the afternoon, bringing some cloud cover and a shower or
two, and will hold temps there down in the 70s.

Saturday will also see increasing southwest winds ahead of the
next system. Widespread gusts of 30 to 40 mph are expected
across the state. This southwest flow will also be modified
desert air, so humidity levels will be falling to 5 to 10
percent across a wide swath of the state. These will result in a
near-critical fire weather day across the state.

The ridge shifts to the east Saturday night, shifting the
moisture tap from the southwest across a larger part of western
WY. The first piece of the western trough races across the
state, bringing a good chance for showers and thunderstorms.
The southwest flow will continue into the middle of next week,
which is setting up as a pattern where daytime heating sparks
showers and thunderstorms along the highest terrain in the
afternoon, dissipating each evening.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 429 PM MDT Fri Jun 5 2026

Upper-level high pressure over WY today has brought very clear
skies with VFR conditions at all TAF sites, and these conditions
are expected to continue through 06Z. Breezy/gusty southwest
afternoon winds will continue at most sites through about
06/02Z, with some gusts over 25 kt. High- level clouds will
move into western WY starting around 06/06Z late this evening
and spread eastward through the night into Saturday morning.
They will thicken as a storm system approaches from the Pacific
Northwest on late Saturday into Sunday. Mid- level clouds are
also expected across western and northwestern WY Saturday, but
VFR conditions should prevail. As moisture increases through the
day, northwest WY from the Tetons to the northern Absarokas and
YNP should see some light showers Saturday evening and
overnight into early Sunday morning. Southwest surface winds
will increase by 06/17Z and increase more around 06/19Z to 15-25
kts with 25-35 kt gusts at all TAF sites.

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...
Red Flag Warning from 11 AM to 8 PM MDT Saturday for WYZ280.

&&

$$

UPDATE...Wittmann
DISCUSSION...Straub
AVIATION...McDonald/LaVoie