175
FXUS65 KRIW 090332
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
932 PM MDT Tue Jul 8 2025

.KEY MESSAGES...

- Very hot conditions with widespread 90s and some locations
  getting close to the triple digit mark Wednesday. The lowest
  elevations of the Bighorn and Wind River Basins have a 40-70
  percent chance of 100 degree highs Wednesday.

- Elevated fire weather conditions continue Wednesday. Humidity
  will be very low, but wind gusts will be limited through the
  afternoon.

- Isolated virga showers will also be possible Wednesday. Wind
  gusts of 55 to 60 mph will be the main threat from any shower
  that forms.

- Another round of showers is possible for southern WY near dawn
  Thursday morning, spreading north and east during the
  afternoon. Overall chances of any accumulation remain low. A
  trailing trough from Canada brings cooler temperatures for
  Friday.

&&

.DISCUSSION...
Issued at 100 PM MDT Tue Jul 8 2025

The current H5 ridge centered on the Four Corners will continue
to provide hot temperatures into the day Wednesday. H7 temps
will be 15 to 18C during the afternoon tomorrow, which
translates down to sfc temps in the mid to upper 90s, especially
for the Wind River and Bighorn basins. An approaching shortwave
trough will nudge down the ridge during the afternoon, bringing
enough instability for some isolated showers during peak heating
Wednesday afternoon, mainly along the highest elevations. Sfc
dry air remains low, so getting showers to the sfc will be
tough, but some gusty winds may accompany any showers. The
approach of the trough will also bring some higher wind gusts in
the afternoon, bringing a fire weather threat (see below).

The trough succeeds in chopping off the top of the ridge,
bringing some increased moisture late Wednesday night. Enough
instability comes along with the trough for some showers for SW
WY Thursday morning. The showers then spread north and east
during the afternoon. Most accumulations will remain light, so
some dry lightning could be an issue for SW WY.

Following along behind this system will be a secondary trough
dropping southeast out of Canada Thursday night into Friday.
Showers and thunderstorms will be possible along the cold front
as it sweeps south, mainly east of the Divide. The most
noticeable difference will be the change in temperature, as
highs Friday will be a good 20 to 30 degrees cooler than the
dry desert heat of Wednesday east of the Divide. The colder
temps will likely not reach south and west of the Divide, so
areas from KJAC to KRKS will again reach the lower to mid 80s
Thursday and Friday.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 930 PM MDT Tue Jul 8 2025

VFR conditions throughout the period for all TAF sites. Light
winds and mainly clear skies overnight under the radiational
inversion. Winds and upper level clouds will increase for all
locations after 18-20Z with daytime heating and mixing to the
surface. Most locations will gust up to 18kts with RKS the
highest, peaking at 25kts. Any shower activity will be limited
and not expected on station, but RKS will have the only real
shot from a stray one and random stronger gust of wind in the
late afternoon/evening. Winds will diminish after 01-02Z with
nighttime cooling once again. However, a couple models are
indicating a stronger wind gusting up to 30 plus knots at LND
after 03Z that are of higher reliability. This is reflected in
the TAF currently but will monitor in the next TAF cycle or two.


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

&&

.FIRE WEATHER...
Issued at 137 AM MDT Tue Jul 8 2025

Widespread elevated fire weather conditions return Wednesday as
temperatures increase and critical RHs spread. Wednesday will
be the hottest and driest day, with widespread afternoon RHs 8
to 15 percent. Gusty winds will increase ahead of the next
trough, with frequent gusts reaching 20mph, with higher gusts in
the higher elevations. Red Flag Warnings currently look
unlikely, due to the lack of dry air, gusty winds above 25 mph,
and cured fuels in the same locations.

Overnight Wednesday night, the trough moves into southern WY,
bringing some scattered thunderstorms. Surface humidity remain
fairly low, so some of the lightning may occur outside of any
wetting rainfall areas.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Straub
AVIATION...Lowe
FIRE WEATHER...Straub/Wittmann