587
FXUS65 KRIW 240334
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
834 PM MST Sun Nov 23 2025

.KEY MESSAGES...

- A strong cold front Monday brings gusty west winds, colder temperatures,
  and precipitation chances across the northern half of the
  area. Minor winter travel conditions are possible for Teton
  and Togwotee Passes Monday afternoon and evening.

- Multiple weak weather systems this week bring light snow over western
  Wyoming, with little to no impacts expected.

- There is potential for a larger winter weather system next
  weekend, which could bring the first widespread lower
  elevation snow of the season. Lots of uncertainty at this
  time.

&&

.UPDATE...
Issued at 1138 AM MST Sun Nov 23 2025

Not much change in the forecast for today, with mild late November
temperatures and a very slight breeze for the Wind Corridor. Short-
term focus is on the weather system tomorrow. Latest models suggest
snow starting over the northwest as early as about sunrise. The
heaviest snow occurs with the frontal passage Monday afternoon and
evening. Combined with gusty west winds, there could be some minor
winter travel impacts across Teton and Togwotee Passes mid-afternoon
through the evening. Snow remains confined to the western mountains
and the Bighorn Mountains, with minor accumulations (half an inch or
less) for the western valleys and possibly Johnson/Natrona Counties.
See discussion below for full details on this system.

&&

.SYNOPSIS...
Issued at 1240 AM MST Sun Nov 23 2025

Quiet conditions continue today, before a strong winter storm
moves over the area Monday. This system will lack any moisture
for any widespread precipitation, but western portions and the
northern mountains continue to be the locations with the best
chances for snow (both mountain and valley locations). Winds
will increase Monday morning ahead of the front, with gusty
winds occurring across the forecast area through the afternoon
and evening. The cold front will usher in the first real 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 1240 AM MST Sat Nov 22 2025

Another quiet day across the Cowboy State today, with isolated
areas of fog over portions of Yellowstone NP and the Bear Valley
in far southwestern Lincoln County. These conditions are not
expected to linger as long as they did Saturday and should lift
out by 18Z. Winds will generally be light again today, except
across portions of Natrona County where gusts around 25 mph will
continue. These gusts will subside by 18Z. Daytime temperatures
will be slightly warmer and make it the warmest day of the
upcoming week. Enjoy these conditions because winter will
finally come knocking Monday.

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
between 18Z and 00Z. The sfc pressure gradient will tighten in
response to the approaching front, with gusts increasing to 20
to 35 mph over northwestern portions before sunrise Monday
morning. This trend will continue through the morning hours and
become more widespread. Westerly winds of 30 to 45 mph will be
common across areas west of the Divide by midday, as well as
portions of Natrona County. Locations like Cody and Dubois will
also be included, with the higher winds occurring at Dubois.
These winds will continue to spread across areas east of the
Divide through the afternoon, as the front begins to move over
northern portions. Winds will then turn northwesterly in the
wake of the front, continuing to gust 25 to 40 mph through much
of the night Monday night. Locally higher gusts around 45 mph
will occur over northern Johnson County. Winds will continue to
decrease from west to east Tuesday morning, possibly lingering
over portions of Johnson and Natrona counties through the
afternoon. As mentioned in previous discussions, any
precipitation will be very limited due to a lack of available
moisture. This will be due to a closed low currently over the
Four Corners that will be exiting over the Central Plains ahead
of this incoming system. Precipitation chances over western
portions will be limited Monday morning, with only a dusting of
snow expected. Chances will increase through the afternoon and
expected to stay as snow in the Jackson Valley, despite expected
afternoon temperatures in the upper 30s. This will be due to
700mb temperatures around -6C (which puts snow levels around
5500ft). These warmer temperatures will obviously limit any
accumulation. Forecasted snowfall amounts remain in the 1 to 3
inch range in the northwestern mountains, and a half inch to 1
inch in the Jackson Valley. Precipitation chances will increase
over northern portions toward the latter half of the afternoon,
as the cold front begins to drop southward. 1 to 3 inches are
also expected over the Bighorns, with the higher end of this
range occurring on the northern end of the mountains. A dusting
of snow, less than 1 inch, is also expected across portions of
Johnson and Natrona counties Monday night as the cold front
rushes through. Due to the timing of the front, temperatures
will only be about 5 to 10 degrees cooler with readings in the
40s to lower 50s. Western portions will be on the colder side of
that range.

Highs on Tuesday will be 10 to 20 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 also allow
for embedded shortwaves to bring chances for snow over the
western mountains Wednesday and Thanksgiving Day. Temperatures
will moderate slightly Wednesday, but return to more seasonal
readings for Thanksgiving Day. Little to no travel impacts are
expected Wednesday and Thursday.

There could be a minor shortwave moving over the area Friday,
ahead of the main storm system. This would bring chances for
snow over mainly northern portions. Model solutions remain in
flux for the next winter storm next weekend. This system looks
to be much stronger than Monday`s storm, with better chances for
widespread snow and colder temperatures.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 357 PM MST Sun Nov 23 2025

VFR conditions will prevail through the period at most terminals. A
weather system begins to push in from the northwest by Monday
morning. This will bring BKN high clouds to most terminals
overnight. Increasing precipitation chances will also spread into
KJAC by around 14Z Monday, with a 30 to 40% chance of snow showers
at KJAC through 18Z Monday. Through those morning hours, most of the
snow showers will be over the mountains, with occasional snow
showers impacting KJAC, and thus have continued with a PROB30 group.
With this, expect frequent mountain obscurations after 12Z Monday
across the northwest WY mountain ranges. By mid-day hi-res models
indicate a break in the snow shower activity though mountain
obscurations will persist. Another round of showers look possible
later in the afternoon for KJAC.

Winds will also increase ahead of this weather system late Monday
morning for most terminals. Gusts 25 to 30kts will be common at most
terminals by 19Z Monday afternoon. A cold front will also be poised
to push through the region, moving through KCOD by around 22Z, and
KWRL towards the end of the period, around 00Z. Lower clouds and
precipitation are also possible to accompany this front, along with
gusty north winds, but most impacts will be after 00Z 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
SYNOPSIS...LaVoie
DISCUSSION...LaVoie
AVIATION...Hensley