159
FXUS65 KRIW 300013
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
613 PM MDT Mon Jun 29 2026

.KEY MESSAGES...

- Light rain/mountain snow continues over northwestern Wyoming,
  ending through the rest of the evening.

- Gusty winds will also begin to subside through the evening,
  with the strongest gusts occurring through 8PM.

- Another night of cool temperatures tonight. Western valleys
  and basins will likely see a frost, with lows in the mid-20s
  to mid-30s.

- Trending warmer this week. Dry and breezy conditions bring
  elevated fire weather concerns. Rain chances will occur, but
  are very limited, so most areas remain dry.

&&

.UPDATE...
Issued at 1231 PM MDT Mon Jun 29 2026

Most of the area remains dry today. Some very light snow over the
western mountains continues through today, though most has already
occurred this past morning. Winds are the main forecast point today,
with widespread gusts 25 to 50 mph for the area. Wind prone
locations see gusts to around 60 mph.

Another night of cooler temperatures, with western valleys and
basins seeing similar lows tonight as last night, in the mid-20s to
low-30s. East of the Divide, lows are in the upper-40s, which could
impact some sensitive plants. Tuesday begins a warming trend, with
highs around 10 degrees warmer than today.

&&

.DISCUSSION...
Issued at 200 AM MDT Mon Jun 29 2026

WV imagery continues to show the deep elongated trough across
the Rocky Mountain West, with colder cloud tops through the CWA
depicted on IR. Weak, distorted fingers of the PFJ aid in
supporting the mainly closed low over MT with divergence aloft
lacking in strong support of any significant weather. A minor
S/W is pushing through the CWA overnight giving way to a few
light rain showers stretching from eastern Sweetwater northeast
to Johnson County that will slowly push east out of the area by
sunrise Monday morning. Limited in rainfall if any, due to dry
surface conditions, will mainly see an impact of lower cloud
cover through a couple hours post-sunrise. Less clouds west of
the Divide will give way to better radiational cooling to allow
for colder temperatures. Western valleys will see near freezing
to just below freezing temperatures near sunrise, but only
touching it for less than hour not needing any cold temperatures
hazards. The coldest spots will be the usual Upper Green River
Basin from Pinedale to Bondurant. Beyond the temperatures, the
next subtle mid-level trough will give way to some light snow
above 10kft for western mountains, highest for the Tetons and SW
Yellowstone of 2-3 inches (50-60%). Other parts of Yellowstone
to the Gros Ventres and Winds could see an inch or so but lower
confidence (30-40%). CAMs seem to be a bit bullish on these
amounts with much of the impacted areas into MT, to include the
Beartooth Pass.

Impacts east of the Divide will be of course wind, with the
passing shortwave. Increasing gusts by mid-morning over 30 mph
to peaking at over 50 mph by noon time. Highest wind speeds
expected for the wind prone areas from eastern Sweetwater to
Natrona Counties to include South
Pass/Greens/Rattlesnakes/Casper Mountain that have a decent
chance to breaking 60 mph (30-40%), but not worthy of any wind
products for these higher elevations. Other areas of note will
include the Cody/Lander Foothills pushing 50 to 55 mph that will
keep an eye on to hit high wind criteria of 58mph (~10-15%).
Winds will of course, decrease towards sunset Monday evening but
remain elevated in these same areas through about midnight.
Monday afternoon will also be the "coolest" day of the week,
with 70s east of the Divide and 50s mainly to the west
(Yellowstone down to the 40s, and even upper 30s for the
northeastern part for Lamar Valley). The ample herds of Buffalo
will welcome the reprieve of the heat.

Beyond Monday, expect a warming and mainly dry trend for the
rest of the week and into the holiday weekend of America`s 250th
birthday celebration. The aforementioned upper level trough will
fill with decreasing divergence aloft and push northeast. The
West Coast will have another deepening L/W trough set up and
remain with weak ridging to the east of the CWA. A few subtle
shortwaves will push to the north and northeast of the area that
will see some weak chances for northern mountains of the
Absarokas and Bighorns (20-30%), but storm activity looks to be
limited to the higher elevations with minimal accumulations
expected. The other thing to keep an eye on will be increasing
fire weather risk with warming temperatures/lower humidity
values, but no significant wind looks to be forecasted beyond
Monday. Independence Day and entire weekend looks to be a
seasonable to just above seasonable day in terms of
temperatures, with afternoon highs into the 80s east of the
Divide and 70s to the west. Limited storm chances look to be
confined to just the northern Bighorns, but stay tuned for any
updated forecast changes in the coming days.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 353 PM MDT Mon Jun 29 2026

Rain showers will continue into the early evening for KJAC,
where low clouds and MVFR visibility has been reported recently.
Precipitation is forecast to decrease and ultimately end before
sunset, with clouds slowly clearing overnight.

Elsewhere, gusty west winds will continue through sunset. KCPR
has seen gusts in the 50 kt range, with other locations seeing
gusts in the 30 kt range. Expect winds to decrease quickly
after sunset at all terminals.

Skies become more clear and winds will be lighter on Tuesday.

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

&&

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

&&

$$

UPDATE...Wittmann
DISCUSSION...Lowe
AVIATION...VandenBoogart