Riverton, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

361
FXUS65 KRIW 222257
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
357 PM MST Mon Dec 22 2025

.KEY MESSAGES...

- Snow tapers off tonight, with additional snowfall amounts of 3
  to 6 inches expected, mainly for the highest elevations.

- Winds of 35 to 45 mph continue, with locally higher wind gusts
  of 60 to 70 mph near Casper/Casper Mountain and over South
  Pass/Red Canyon, respectively late this morning into early
  afternoon. Winds will decrease late this afternoon into the
  evening.

- Rainfall amounts of 0.20" to 0.30" expected in the western
  valleys.

- Above normal, possibly record high, temperatures, and windy
  conditions Monday through Christmas.

&&

.UPDATE...
Issued at 125 PM MST Mon Dec 22 2025

Moisture continues to stream northeast across the state, and
continues to wring out with snow across the western mountains.
Snow rates have been decreasing, as the main moisture plume
shifts away from the region. Winter Storm Warnings are scheduled
to end at 5PM tonight, and with minimal additional snowfall and
decreasing winds expected, likely will not need any extensions.

Winds have been gusting 40 to 50 across central WY this
afternoon, but have been tapering off in the past hour or so.
Winds are expected to stay under 50 mph the rest of the
afternoon, so will not be posting any further High Wind
Warnings.

No change in the week`s forecast as well, with lower elevations
temperatures holding in the mid to upper 50s (!), and some
light rain forecast on Christmas Day.

&&

.DISCUSSION...
Issued at 122 AM MST Mon Dec 22 2025

First order of business: forgot to mention in the discussion
yesterday of the Winter Solstice, which occurred at 8:03AM Sunday
(a lot of weather to discuss yesterday). Days are getting
longer.

Moderate to heavy snow continues over the western mountains as of
07Z this morning and will continue through the rest of the day
today. Additional snowfall amounts of 6 to 8 inches expected, with
locally higher amounts up to 15 inches over the Tetons, Gros Ventres
and the Pitchstone Plateau in southwestern YNP. Winds will decrease
through the afternoon as well, with gusts of 25 to 35 mph expected
by sunset. Temperatures in the valleys will stay above freezing
through the day today, even as snow levels drop closer to 7000ft.
Liquid precipitation amounts will be much less today, with an
additional 0.20" to 0.30" expected. Snow will continue this evening,
along with the gusty winds up to 35 mph. Additional amounts up to 6
inches expected. The snow and wind will decrease late tonight after
06Z Tuesday.

The story for the rest of the CWA will once again be gusty winds and
above normal temperatures. The breaking mountain wave that was
expected at Lander occurred at 0643Z with a 59kt (68 mph) peak wind
gust. Red Canyon also had a 107 mph gust at 0116Z (616pm Sunday
evening). These high winds are not expected today, but will still be
in the 60 to 70 mph range. Lander could also have another breaking
mountain wave between 17Z and 21Z. Otherwise, southwest winds will
increase late this morning into the afternoon, with widespread gusts
of 35 to 45 mph once again over most of the CWA. The places least
impacted by these winds will be eastern portions of the Bighorn
Basin and northern Johnson County, with the latter area being
impacted by a weak cold front dropping southward during the
afternoon. Locally higher wind gusts close to 60 mph will also
return to Casper Mountain and the south side of Casper (Hwy 258).
These winds will help drive temperatures to above normal levels
again, with readings in the 50s for much of these areas. Rock
Springs reached 58F Sunday, tying the all-time highest temperature
in December (which was set in 2021). Some areas could reach 60F
today, namely, Casper, Riverton, Thermopolis, Worland, Kaycee and
Manila/Flaming Gorge.

Winds will decrease across much of the area this evening, with gusty
winds of 35 to 45 mph will continue over the mountains and portions
of Sweetwater and Natrona counties. The aforementioned cold front
will get stalled out north of Kaycee and Linch late tonight, before
the southwest winds wash it out.

The impacts from the Atmospheric River will finally end Tuesday, as
a ridge begins to build over the region. This will lead to another
day of above normal temperatures (with record high temps expected
again), with highs in the 50s to near 60 degrees. Any precipitation
will be confined to far northwestern portions in the morning, as the
ridge shunts most of the moisture to the north and west. Winds will
be similar to today, with gusts of 30 to 40 mph occurring across
much of the CWA through the afternoon again. Locally higher gusts
could occur at KCOD. Dry and windy conditions are likely again
Christmas Eve, with record high temperatures possible once again as
the southwest flow aloft continues. Rain and snow returns to western
portions by Wednesday evening, as a lead shortwave moves over the
region. Rain showers could spread across southern portions through
the overnight hours into Christmas morning. Confidence for western
portions to have a White Christmas have gone down, as snow levels
will start around 8000ft again, possibly dropping to 7000ft after
sunrise Christmas morning. The warm and windy conditions will also
return for Christmas for the rest of the CWA.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 356 PM MST Mon Dec 22 2025

West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals.

Rain around KJAC should end by 10z/Sun, but could end as early as
about 04z/Sun. In any case, chances will be diminishing to begin the
period. MVFR to brief IFR conditions are possible with this rain,
but should improve to VFR after rain ends. Elsewhere, winds are
light overnight, increasing late Sunday morning, with VFR conditions.

East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals.

Gusty west to southwest winds should decrease this evening, with
lighter winds overnight. Winds increase Sunday morning, with gusty
winds most locations for Sunday afternoon. Otherwise, VFR conditions
expected.

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

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 5 PM MST this afternoon for WYZ001-
002-012-014-015-024.

&&

$$

UPDATE...Straub
DISCUSSION...LaVoie
AVIATION...Wittmann