982
FXUS65 KRIW 091520
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
920 AM MDT Tue Jun 9 2026

.KEY MESSAGES...

- The greatest coverage for showers and thunderstorms today will
  be across western Wyoming and from Sweetwater to Natrona
  Counties. Isolated to widely scattered showers and
  thunderstorms elsewhere.

- Widespread strong southwest winds through late tonight with
  gusts of 25 to 35 mph. Strong west to northwest winds and
  widespread gusts of 35 to 45 mph all day Wednesday.

- Elevated to near critical or critical fire weather conditions
  through Wednesday night due to gusty winds and low relative
  humidity. A Red Flag Warning is in effect for portions of
  Natrona County until 8PM Wednesday.

-Near normal temperatures, breezy, low humidity, and limited
 rain and thunderstorm chances (less than 30 percent) Thursday
 through Saturday.

&&

.DISCUSSION...
Issued at 130 AM MDT Tue Jun 9 2026

WV imagery continues to show the Pacific northwest upper level
trough to the west with the PFJ extending cyclonically through
Idaho and into Montana. Jet max of around 120kts continues to
deepen the disturbance with ample diffluence aloft. IR shows
the cooler cloud tops inching closer to the WY/ID state line
that will slowly makes its way west of the Divide bringing with
it increasing shower activity by sunrise Tuesday morning
expanding to the Divide by late morning. Widely scattered
showers and possible isolated thunderstorms through much of the
day Tuesday, but with less instability compared to Monday that
should see minimal lightning activity in regards to fire
weather concerns. Currently, QPF amounts do not look substantial
and some mountain snow west of the Divide to include the Winds
in the highest of the elevations about 11-12kft. Nothing of note
amount wise but intriguing for June and those in the
backcountry enjoying the Wyoming great outdoors. It will be
helpful for Gannett Peak climbers later in the month keeping the
infamous bergschrund closed into early July before it starts
its slow opening making for harder glacier travel. The Bighorns
will look to get in on the action by Tuesday afternoon as
upslope rain shower activity expands east of the Divide for the
higher elevations but no snow looks to come to fruition not
being as high in stature.

The best chance for storm activity will come mid to late
afternoon along the west to east moving cold front clashing with
the drier warmer air to the east. The cold front looks to cross
the Divide towards sunset Tuesday evening pushing east of the
CWA before midnight. This will limit and storm development with
more of a lack of moisture content east of the Divide losing the
daytime heating Tuesday. Cooler temperatures west of the Divide
with earlier FROPA, but temperatures consistent with Monday for
points east. Wednesday will be the coolest day of the week with
more seasonable temperatures expected CWA wide as the upper
level disturbance shifts more northeastward bringing the
precipitation chances limited to northern areas of the CWA from
Yellowstone across the northern Absarokas and Bighorn Basin to
the Bighorn Mountains themselves. Shower activity will exit to
the east and northeast by late Wednesday evening and becoming
mostly dry overnight into Thursday. Diurnal shower activity for
higher elevations expected Thursday afternoon/early evening for
Thursday onward as northwest flow aligns back across the
northern Rockies. Upper level ridging builds back in across the
western United States with increasing convergence aloft to aid
in a warming trend Friday and into the weekend.

The other weather element to expect will be winds for Tuesday
and Wednesday. Ahead of the aforementioned cold front, expect
gusty southwest winds, strongest east of the Divide with gusts
up to 40-55mph and in particular the usual wind corridor from
Sweetwater to Natrona and Johnson Counties from late Tuesday
morning through much of the day. Behind FROPA, expect a shift to
west/northwest winds continuing to be quite gusty but not as
strong into the overnight hours through Wednesday morning.
These winds will once again pick up by late in the morning
through sunset before finally subsiding towards sunset and
overnight into Thursday as skies improve allowing for more
radiational cooling and inversion to set up near the surface.
Thursday onward, expect light winds but still breezy back to
normal for Wyoming through the end of the week and over the
weekend. Northwest to west upper level flow continues into next
week with longer term model solutions showing the next best
chance for a bigger weather disturbance come mid following week.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 430 AM MDT Tue Jun 9 2026

VFR conditions expected for much of the period at all locations.
Increasing clouds across the entire CWA ahead of the next
shortwave and associated cold front. Rain pushes in at JAC early
in the period spreading to the Divide by mid morning around 15Z.
MVFR ceilings possible with rain at JAC through 17Z as winds
increase as well. Gusts up to 25kts will be common, peaking at
locations east of the Divide up to 30 to 40 kts. TAF sites east
of the Divide look to remain dry as winds diminish after sunset
around 03-05Z but will increase once again at CPR towards the
end of the period and other sites into the next TAF cycle.

Thunderstorms likely west of the Divide with aforementioned
cold front west of the Divide after 20Z with FROPA but diminish
as it pushes east shifting winds from westerly to north of
westerly there after.

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

&&

.FIRE WEATHER...
Issued at 130 AM MDT Tue Jun 9 2026

Near critical to critical fire weather conditions expected for
Tuesday and Wednesday from 9AM to 8PM both days. Red Flag
Warning continues for Fire Zone 280 (only zone with critical
fuels at this time). Strong winds expected out of the southwest
to north of west gusting up to 40 to 55 mph in many areas east
of the Divide, and up to 30 to 40 mph to the west. Humidity
values will be as low as 10 to 15 percent, driest in the Wind
Corridor from Sweetwater to Natrona Counties.

Low humidity values continue for Thursday and Friday into the
weekend, but with less wind expected seeing only breezy
conditions up to 15 to 25 mph.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM MDT Wednesday for WYZ280.

&&

$$

DISCUSSION...Lowe
AVIATION...Lowe
FIRE WEATHER...Lowe