646
FXUS65 KRIW 201106
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
406 AM MST Thu Nov 20 2025

.KEY MESSAGES...

- Isolated showers (20-40%) linger across portions of western
  and southern WY this morning.

- Patchy areas of fog will be possible this morning across
  portions of western and central WY.

- Another round of showers may be possible Friday mainly over
  central and southern WY.

- Dry and quiet conditions build in for the weekend with a push
  of colder air possible for the first half of next week.

&&

.DISCUSSION...
Issued at 237 AM MST Thu Nov 20 2025

A slight shift in the forecast compared to the previous discussion
from yesterday. The main difference is increased coverage and
chances for showers across portions of central and southern WY
through the rest of the morning. The best chances (20-40%) will
remain over western WY with lesser chances (10-30%) for portions of
central and southern WY. This change in the forecast is due to a
slightly farther north track of a weakening upper level low moving
out of the southwestern CONUS at this time. This shift in the track
will also lead to increased chances for showers early Friday morning
through the afternoon. Parts of southern and central WY look to have
the best chances (20-40%) for periodic showers Friday. Overall, the
showers today and Friday will have minor impacts. The greatest
impacts would be in the higher elevations of central and
western mountain ranges where a coating to an inch of snow may
be possible. Another thing to monitor this morning will be
patchy areas of fog. The locations with the best chances
(20-40%) of seeing fog are western valleys such as Star Valley,
Jackson Hole and portions of the Upper Green River Basin. Other
locations include central WY such as the Wind River Basin along
with parts of Natrona County. Any areas of fog that do develop
this morning should gradually dissipate through the morning into
the early afternoon today.

Other aspects of the near term forecast remain mostly unchanged.
Temperatures still are forecast to sit at or slightly above
seasonable values. Highs through the weekend range from the low to
mid 40s west of the Divide and low to mid 50s east of the Divide.
Winds look to be light through this period with maybe a slight
breeze in wind prone locations. As for precipitation, after Friday
high pressure tries to build in over the region, leading to mainly
quiet and dry conditions through the weekend.

The upcoming Thanksgiving week forecast is looking quite tricky
with lots of moving parts and little consensus among model
guidance. The first half of the week will see another
disturbance shift south and east out of the PACNW. This
disturbance looks to have cold air associated with it and the
track will determine just how cold it may get. Models differ
with some having the axis digging south leading to colder air
here. Other models have it further east leading to the coldest
temperatures east of the area. The timing of this cold air would
be around Tuesday into Wednesday with some chilly morning lows
possible these days. Another aspect with this disturbance will
be whether or not we see any widespread precipitation. Similar
to the degree of cold air, the track of this disturbance will
lead to differing impacts in terms of precipitation. The second
half of the week sees the active pattern continue with another
potential disturbance moving into the area. However, just like
the first half of the week, the track of this disturbance will
lead to greatly differing impacts. Being nearly a week out there
is even greater uncertainty regarding what we can expect here
in the Cowboy State.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 400 AM MST Thu Nov 20 2025

Areas of fog and IFR to LIFR conditions at JAC/PNA/BPI/CPR
through about 16-17Z. VFR thereafter to join all other TAF sites
with mid level ceilings through the afternoon before scattering
out by evening and overnight. Some low stratus possible for
PNA/BPI with upslope conditions, as well as CPR advecting in
from the east. Confidence lower for Friday morning with fog
development as conditions push further east. Otherwise, light
winds 10 kts or less through the entirety of the period for all
locations.

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.

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...Lowe