448
FXUS65 KRIW 220757
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1257 AM MST Sat Nov 22 2025

.KEY MESSAGES...

- Fog and low clouds will remain in place in far western
  portions this morning, mainly from Star Valley south along
  western Lincoln County, as well as portions of Yellowstone NP.

- Temperatures in the 40s to lower 50s through the weekend.

- A strong cold front will push through Monday into Monday
  night, with increasing precipitation chances for northern and
  northwestern Wyoming. Lows will drop into the teens Monday
  and Tuesday night.

- A much more active weather pattern will set up next week, but
  weather impacts should remain minimal for Wyoming until next
  weekend.

&&

.SYNOPSIS...
Issued at 1246 AM MST Sat Nov 22 2025

Quiet conditions continue over the weekend, before a strong
winter storm moves over the area Monday. This system will lack
any moisture for any widespread precipitation, but initial
indications continue to be for snow (both mountain and valley
locations) across western portions through the day. Winds will
increase Monday morning ahead of the front, with gusty winds
occurring across the forecast area behind the front. The front
will usher in the first taste of winter, with highs on Tuesday
remaining in the 30s for much of the area. Northwest flow aloft
will keep conditions a bit breezy through the middle of the
week, before another winter storm potentially impacts the region
next weekend.

&&

.DISCUSSION...
Issued at 1246 AM MST Sat Nov 22 2025

Another quiet day across the Cowboy State today, with periods of
high clouds through the morning. Areas of fog are not expected to be
as widespread as in recent days and be mostly confined to
Yellowstone NP, the Star and Bear Valleys and areas near Farson.
Any fog will lift out by late morning. Winds will generally be
light today as well, with gusts around 15 mph occurring mainly
for portions east of the Divide for a few hours through the
afternoon. Daytime temperatures will be similar to Friday, with
highs in the 40s to lower 50s. Similar conditions will return
Sunday, although fog is not expected to develop. Clouds will
increase over southern portions tonight into Sunday morning from
a closed low moving over the Four Corners region. Winds will
continue to be light, with gusts around 15 mph being more
confined to areas west of the Divide. Enjoy these conditions
because winter will finally come knocking.

A storm system will move onshore over the PACNW Sunday night,
continuing toward the Northern Rockies Monday morning. The
associated cold front will reach far northwestern portions by
18Z and quickly progress over the CWA through the day and
evening, reaching southeastern portions of the state by 06Z
Tuesday. The main impact from this system will be wind and
colder temperatures. Any precipitation will be very limited
along the front, due to a lack of available moisture. This will
be due to the aforementioned Four Corners closed low that will
be exiting over the Central Plains ahead of this incoming
system. Western portions of the forecast area continue to show
to have the best chances for precipitation, which will likely be
snow. If precipitation does start out as rain in the lower
elevations, it is expected to quickly change over to snow.
Initial snowfall amounts are only 1 to 3 inches in the
northwestern mountains, as well as the Bighorns, and a half inch
to 1 inch in the Jackson Valley. If future model trends slows
the timing of the front and the precipitation occurs late in the
afternoon into the evening, any potential changeover from rain
to snow could introduce the threat for black ice. However, the
likelihood of the precipitation starting as snow during this
timeframe due to falling temperatures would increase.

Winds will gradually decrease across the CWA Monday night,
subsiding from west to east as the system continues its eastward
progression over the Northern/Central Plains. Highs on Tuesday
will be 5 to 15 degrees colder, with readings in the 30s for
most locations. Northwest flow aloft will be in place over the
Cowboy State, as a broad ridge develops over the PACNW. This
will keep conditions breezy across southern portions and Johnson
and Natrona counties. This pattern will allow for embedded
shortwaves to bring chances for snow over the western mountains
Wednesday and Thanksgiving Day. Temperatures will moderate
little Wednesday, but return to more seasonal readings for
Thanksgiving Day. Little to no travel impacts are expected
Wednesday and Thursday.

Model solutions remain in flux for the next winter storm next
weekend. The faster solution has this system beginning to impact
the CWA by Friday, which seems a bit too fast. This system
looks to be a bit stronger, with better chances for widespread
snow and colder temperatures (even colder than Monday`s storm).
Winter is finally coming.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1015 PM MST Fri Nov 21 2025

VFR conditions at TAF sites through the next 24 hours, with only
high cirrus sweeping in from the north. Some low clouds are
trying to move into KJAC, but are not expected to get over the
Tetons. Some low clouds and fog are possible in far southwest WY
(KEMM/KAFO) into early tomorrow morning. Most sites will have
only light winds tonight and tomorrow, with only KCPR/KCOD
seeing gusts approaching 15kt.

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.

&&

$$

SYNOPSIS...LaVoie
DISCUSSION...LaVoie
AVIATION...Straub