907
FXUS65 KRIW 210947
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
247 AM MST Fri Nov 21 2025

.KEY MESSAGES...

- Areas of fog have developed this morning across parts of
  southwestern and northeastern WY.

- Near to slightly seasonable temperatures persist across the
  state today with a few isolated showers (10-20%) possible
  over far southern WY.

- Quiet and dry conditions are expected to prevail through the weekend
  with colder temperatures and precipitation chances possible
  for the start of next week.

- Light snow may be possible across western WY with quieter
  weather elsewhere for Thanksgiving, but at this time
  confidence still remains low.

&&

.DISCUSSION...
Issued at 200 AM MST Fri Nov 21 2025

Areas of fog return to portions of the state this morning. Fog
has already begun to develop across parts of Natrona, Johnson,
Sweetwater and Lincoln Counties as of early this morning. Other
locations in Sublette and Fremont counties may see fog develop
through the rest of the morning with chances around 10-30%. As a
result of the fog, visibilities may drop below one mile at
times, which may create difficult driving conditions. Areas of
fog should begin to dissipate by the late morning with clearing
expected by the early afternoon. Besides fog this morning, a
few isolated showers will be possible today with the best
chances (10-20%) being across far southern WY. Precipitation
chances and coverage has decreased due to the disturbance moving
south of the state becoming more disorganized than originally
thought. Overall, most locations look to remain dry with skies
expected to gradually clear out through the day.

Ridging looks to build in over the region for the weekend. This will
keep a newly developed cutoff low currently over the Desert
Southwest far to the south of the state. As a result, dry and
mostly quiet conditions prevail across the Cowboy State through
the weekend. Near to slightly above seasonable temperatures
persist across the state today and through the weekend. Highs
will range in the low to mid 40s west of the Divide and low to
mid 50s east of the Divide. Winds remain light over the next
couple of days with periodic breezes possible in wind prone
locations.

Active weather is looking more likely to return for the start of
next week. The setup looks to be a potent Pacific disturbance that
moves onshore across the PACNW late Sunday. This disturbance then
begins to pull cold air down south from Canada as it continues
to track east. The timing of this currently is expected to
occur during the day Monday into Tuesday. The best chances for
precipitation would be across western and far northern WY as a
result of post frontal orographics. A few showers may be
possible along the front as it moves across the state but
chances look limited due to a lack of available moisture.
Snowfall amounts look minimal, with a quick inch or two possible
in the mountains and a light coating for lower elevations.
Winds are forecast to increase Monday as well with gusty
conditions possible, especially in wind prone locations. As a
result of this system, temperatures drop quickly Monday as the
front moves through. Models are indicating some of the coldest
temperatures so far this season for Tuesday and Wednesday. The
exact degree of the cold still remains uncertain at this time,
but a better idea of what to expect should come into better view
by the weekend. The second half of the week, including
Thanksgiving, at this time looks active mainly for western and
northwestern WY. Another disturbance moves into the region
possibly leading to snow chances for western mountains and
valleys. However, there still remains high uncertainty regarding
impacts as the timing and track of this disturbance can easily
shift over the next few days. Overall, it will be worth
monitoring especially if planning to travel over any western
mountain passes for Thanksgiving.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1013 PM MST Thu Nov 20 2025

Moisture is slightly more limited tonight versus last night,
which will limit fog formation. Most TAF sites will see minimal
fog, mainly at KBPI/KPNA and at KCPR, but any impacts will be
more brief than last night. There is an outside chance that fog
off of Boysen Reservoir may reach KRIW around sunrise, but any
fog here will be shallow and patchy. Other airport sites at
KBYG, KEMM, and KAFO are already seeing fog in the vicinity, and
will continue through the rest of the night. KRKS is
fluctuating due to passing light rain/drizzle, which will
continue through the night. After sunrise, any remaining low
clouds will thin out except for KRKS/KEMM, which will hold on
through around noon before lifting. Minimal cloud cover remains
through the rest of the day and into Friday night.

&&

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

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...Straub