490
FXUS65 KRIW 271830
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1130 AM MST Thu Nov 27 2025

.KEY MESSAGES...

- Light snow showers are possible across the western mountains through
  mid-afternoon. Otherwise, today is mostly sunny with mild
  temperatures today.

- A cold front will bring snow and gusty north winds to much of
  the area Friday through Friday night. Winter travel
  conditions are possible during this time.

- Much colder temperatures expected through the weekend with
  lows dropping to near zero east of the Divide.

&&

.UPDATE...
Issued at 1128 AM MST Thu Nov 27 2025

Snow showers are on a decreasing trend over the western mountains.
These should clear out by the end of the afternoon, with little to
no additional accumulations. The rest of the day remains unchanged,
with mild temperatures across the area. Still watching the system
for late Friday into early Saturday. Winter travel impacts are still
possible in this time frame, especially east of the Divide where
falling snow and a gusty north wind could limit visibilities at
times. Conditions improve through the day Saturday.

&&

.DISCUSSION...
Issued at 339 AM MST Thu Nov 27 2025

The next shortwave within the northwest flow over the area is
entering western Wyoming early this morning. With warm air advection
and a little moisture funneling up the Snake River Plain, this will
bring a quick shot of snow through the morning hours across western
Wyoming. More specifically, light snow should fall from the Star
Valley area to Pinedale northward to the Montana border. Recent high
resolution model guidance has trended accumulations up slightly,
most notably across the Tetons which should pick up 2 to 4 inches by
mid-morning. Impacts are expected to be minor and mainly limited to
Teton Pass. Snow will end for most by noon save for some light
upsloping snow showers across the mountains with little additional
accumulation. Otherwise, most locations will see a partly sunny
Thanksgiving with warmer than normal temperatures, generally peaking
into the 40s across lower elevations.

A more widespread snow event is on the way for Friday. The northwest
flow will give way to a trough that will drop south out of Canada
into the Pacific northwest tonight, approaching Wyoming by Friday
morning. Near the surface, an associated cold front will move north
to south across Wyoming beginning mid-morning. Snow will follow this
trend, spreading north to south across most of the area Friday
afternoon through Friday night. The placement of the trough will
keep snow most widespread east of the Divide, though a lack of more
robust moisture (PWATs in the 0.2-0.4 inch range) will keep
accumulations on the lighter side. Most locations east of the Divide
will have a 50-60% chance of at least an inch of snow, though those
odds drop to 20-30% for over 2 inches. The exception may be across
eastern Fremont County through Natrona County, where an upsloping
component and jet streak late Friday night could lead to slightly
higher totals in the 2 to 4 inch range. On the high end, there is
around a 10% chance of the Highway 20/26 corridor between Moneta and
Casper seeing around 6 inches. The mountains will be most favored,
of course, including the Tetons, Absarokas, and Bighorns where
totals will fall in the 4 to 6 inch range (20-40% chance of more
than 6 inches). The heaviest period of snow is expected after sunset
Friday through the pre-dawn hours Saturday. Along with the snow,
there will also be a gusty north wind Friday night as a stronger,
colder frontal surge arrives. This could lead to some visibility
issues east of the Divide, especially in any snow bands that
develop.

Snow will come to an end Saturday morning, leaving a much colder
weekend in the wake of the system. Highs will only peak into the 20s
for most locations east of the Divide where the coldest air will
intrude. Lows Saturday morning through Monday morning will be the
coldest of the season, dropping to near zero east of the Divide.
Otherwise, guidance has been persistently showing a quick midlevel
low clipping southwestern Wyoming on Sunday. This may bring another
shot of light snow Sunday focused west of the Divide. The current
track of this system will keep most of the snow to our south and
west, however, and totals are currently expected to remain under an
inch.

Further out, ensemble guidance keeps a fairly progressive northwest
flow over Wyoming. This favors more seasonable temperatures with
several chances for precipitation across the area through next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1024 AM MST Thu Nov 27 2025

Most precip has ended for this round, but low clouds continue to
hang around this afternoon for KJAC and KPNA. Cigs should remain
above 4000ft, and slowly thinning and lifting through the rest
of the afternoon. These sites, along with KCOD/KWRL and KRKS,
will have midlevel clouds through the rest of the afternoon,
with some improved breaks around 00Z.Remaining sites will inly
note high cirrus through this evening. The next system begins
to move into the northern sites overnight, with increasing
midlevel cloud decks by 12Z for KCOD/KJAC. Most impactful
aviation weather for all sites should hold off until after
12Z/28.

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

&&

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

&&

$$

UPDATE...Wittmann
DISCUSSION...Myers
AVIATION...Straub