082
FXUS65 KRIW 031800
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1200 PM MDT Sun Aug 3 2025

.KEY MESSAGES...

- Red Flag Warning posted for the southwest-quarter of Wyoming
  12 PM to 8 PM Monday. A warm, dry, and breezy week is ahead,
  which will keep fire weather concerns heightened. Thursday and
  Friday may be the windiest days of the week.

- A slight chance of showers and thunderstorms Sunday afternoon,
  mainly between 2 PM and 7 PM. Impacted areas will be the
  Absaroka and Bighorn Mountain Ranges, eastward into the
  adjacent basins.

- Isolated showers and thunderstorms persist over northwest
  Wyoming Monday afternoon.

&&

.UPDATE...
Issued at 1200 PM MDT Sun Aug 3 2025

A transient shortwave ridge will keep convection at bay for many
areas Sunday afternoon and evening as drier air filters into
the region from the Great Basin. The best chance for isolated
to scattered showers and thunderstorms will be across the
Absaroka and Bighorn Ranges downstream into the adjacent basins
between 2 PM and 7 PM. A few showers and storms will linger over
far northern portions of the Absaroka Mountains and Bighorn
Basin until sunset before fading. Otherwise, plenty of sunshine
with seasonal temperatures on this first Sunday of August. A
batch of mid-level cloud cover crosses the region late tonight
and early Monday morning. However, little more than virga, if
even that, is expected as the clouds progress eastward through
mid-morning Monday. However, the remnants of this moisture
combined with a shortwave traversing the Northern Rockies Monday
will reignite convection across the northwest mountains Monday
afternoon. This same shortwave will be responsible for
increasing westerly wind Monday afternoon along and west of the
Continental Divide. Speeds of 15 to 25 mph will be common. Dew
points crater across southwest Wyoming Monday afternoon as the
westerly wind transports very dry surface air into this portion
of the state. Abundant sunshine and 700mb temperatures surging
to +15C to +18C boost surface temperatures to about 3-5F above
normal. This results in single digit relative humidity for
almost the entire southern half of the forecast area. Red Flag
Warnings are in effect across southwest Wyoming, where winds
will be greatest, from 12 PM to 8 PM Monday. The overall trend
is for the warm, dry, and breezy conditions to persist through
Friday, especially across southwest Wyoming. EFI/SOT begin have
started to hint at an uptick in wind speeds Thursday/Friday.

&&

.DISCUSSION...
Issued at 230 AM MDT Sun Aug 3 2025

The H5 ridge continues to build across the greater Four Corners
region, but remaining local moisture will still bring some
showers during the afternoon. The next shortwave will be able to
tap enough remaining moisture to spark a few showers and
thunderstorms mainly for Teton and Park Counties during the few
hours around peak heating this afternoon. Some daytime CU will
also build along the Bighorns, but chances for accumulating
precip there will be minimal. The remainder of the area will see
mostly sunny skies and continued warm temperatures in the mid
to upper 80s.

After today, most of the state transitions into a drier, more
fire-weather concerning regime, as desert air pushes in from the
southwest. Shortwaves will continue to sweep around the northern
edge of the ridge, but will get pushed farther north. They will
be close enough, though, to tighten the gradient for gustier
southwest winds. Monday looking more likely for the combination
of these two for elevated to critical fire weather concerns.
Have opted to go straight to Red Flag Warning for southern WY
for Monday, as confidence in that period looks higher,
especially with humidity levels falling below 10 percent for an
extended period of the day. Tuesday is also looking very dry,
but winds currently forecast to hold back from Monday numbers,
so will not stretch the Red Flag beyond Monday.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1123 AM MDT Sun Aug 3 2025

All terminals to be VFR through the forecast period. The best chance
for Sunday afternoon convection will be at KCOD as isolated showers
and storms move east off the nearby Absaroka Mountains. Cumulus
towers look like they will stay to the north and south of KCPR.
Otherwise, little more than cumulus through sunset. Westerly
surface wind 8-13kts for the western terminals with occasional
gusts around 18kts at KRKS until 02Z/Monday. Mid-level cloud
deck traverses the region late tonight and early Monday morning
producing isolated virga showers.

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 noon to 8 PM MDT Monday for WYZ277>279-
288-289-414-416.

&&

$$

UPDATE...CNJ
DISCUSSION...Straub
AVIATION...CNJ