173
FXUS65 KRIW 051111
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
511 AM MDT Fri Jun 5 2026

.KEY MESSAGES...

- Very warm Friday and Saturday as ridging builds across the
  Rockies. Highs today reach the 80s, with a few low 90s in the
  Bighorn Basin. Temperatures will be even warmer Saturday,
  with highs in 80s and 90s, with a few 100 degree readings
  possible.

- Dry and windy conditions today and tomorrow will lead to
  elevated to near-critical fire weather concerns across the
  state.

- Ridge shifts east next week, bringing better moisture into
  western mountains. Afternoon showers and thunderstorms are
  expected over higher terrain.

&&

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

The trough that has been lingering in the vicinity that 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 /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 510 AM MDT Fri Jun 5 2026

VFR conditions through the next 24 hours, with nearly clear
skies. Winds will increase from the southwest later this
morning, but most areas stay under 15kts. Light winds return
early this evening. A few high cirrus begin to move into western
sites after 06Z/06, but remain above 15000 through 12Z/06.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Saturday morning through Saturday
evening for WYZ280.

&&

$$

DISCUSSION...Straub
AVIATION...Straub