Powell, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

102
FXUS65 KRIW 210854
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
154 AM MST Sun Dec 21 2025

.KEY MESSAGES...

- Snow returns to western portions this morning, as the start of
  a multi- day heavy snow event. Snowfall amounts of 18 to 36
  inches are expected through Monday afternoon.

- Winds of 35 to 45 mph can be expected Sunday and Sunday night,
  adding to the already difficult travel conditions over Teton
  and Togwotee Passes. These winds will also occur from southern
  Lincoln County to southern Johnson County. Locally higher wind
  gusts of 60 to 80 mph will occur near Casper/Casper Mountain
  and over South Pass/Red Canyon, respectively.

- Snow is expected in the western valleys at times this morning,
  but will change over to rain by the afternoon. Rainfall
  amounts of 0.80 to 1.25" will fall Monday afternoon in the
  Jackson/Star Valleys, Hoback Junction and Bondurant as well.
  Ponding of water, and even some icy conditions, will be
  possible tonight, as temperatures drop to near freezing.

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

&&

.DISCUSSION...
Issued at 136 AM MST Sun Dec 21 2025

Light bands of snow over eastern ID are pushing into far western
portions of the CWA, as well as the Upper Green River Basin, as of
07Z. This is the beginning of the incoming atmospheric river that
was discussed in the previous discussion. Overall, little has
changed with that forecast: Precipitation will start as snow in the
Jackson/Star Valleys, with 1 to 2 inches expected before changing
over to rain after 18Z today. This will be due to rising snow
levels, ranging between 7000 and 8000 ft by 00Z Monday. Snowfall
rates over the mountains will quickly increase this morning, with
rates of 2"/hr expected through the afternoon. Periods of moderate
to heavy wet snow will continue tonight into Monday morning,
becoming light Monday afternoon. Will extend the Winter Storm
Warnings to 00Z (5pm Monday) as a result. Precipitable water
values will be close to record values with this event. This,
coupled with favorable west-southwest upslope flow, will lead to
this relatively brief period of heavy wet snow. Snowfall
amounts of 18 to 36 inches, with locally higher amounts close to
40 inches, are expected through Monday afternoon. Rainfall
amounts of 0.80" to 1.25" will fall during this timeframe in
the Jackson/Star Valleys, Hoback Junction and Bondurant as well.
Ponding of water, and even some icy conditions, will be
possible tonight, as temperatures drop to near freezing. If this
wasn`t enough, southwest wind gusts of 35 to 45 mph will be in
place over western portions (including the valleys) by 18Z
creating areas of blowing snow in the mountains. This will add
to an already hazardous situation over Teton and Togwotee
Passes, as well as on the ski slopes. These winds will continue
through the overnight hours tonight into Monday morning. Snow
and wind will begin to decrease late Monday morning, with snow
becoming light in the afternoon and wind gusts decreasing to 25
mph.

Elsewhere, it will be a windy day again today with southwest wind
gusts of 40 to 55 mph from southern Lincoln County to southern
Johnson County. Locally higher gusts of 60 (south side of Casper and
Casper Mountain) to 80 (South Pass/Red Canyon) mph will occur. Some
of these higher winds will also occur over the east slopes of the
Wind River, Absaroka and Bighorn Mountains. Winds will decrease a
bit overnight (30 to 45 mph) tonight and not be as widespread. They
will increase again by midday Monday and be similar to today (gusts
of 40 to 55 mph). There is also a signal these high winds will
impact Lander some time tonight. The timing of this occurring is
difficult due to the nature of a breaking mountain wave. Models are
currently forecasting this to occur sometime between 03Z and 12Z
Monday. Apart from the higher peaks of the Bighorns and the Upper
Wind River Basin near Dubois, areas east of the Divide will stay dry
from this event as the western mountains will keep any moisture from
crossing the Divide. These windy conditions will also lead to above
normal temperatures, with highs in the upper 40s to middle 50s
this afternoon. Highs will approach the 60 degree mark again
Monday, namely the Casper area, Riverton, and southern portions
of the Bighorn Basin and Johnson County.

The impacts from the Atmospheric River will continue to wane
Tuesday, as a ridge begins to build over the region. This will lead
to another day of above normal temperatures (record high temps
likely), with highs in the 50s to near 60 degrees. Any precipitation
will be confined to far northwestern portions, as the ridge shunts
most of the moisture to the north and west. Dry and windy conditions
are likely again Christmas Eve, with record high temperatures
possible once again. Another storm system looks to be moving onshore
over the PACNW on Christmas Eve/Christmas, possibly impacting
western portions with a White Christmas.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1029 PM MST Sat Dec 20 2025

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

The next weather system is quickly approaching western Wyoming. KJAC
is expected to see MVFR to IFR impacts starting by 11Z. KBPI and
KPNA will follow by 14Z as snow moves east. These conditions should
last through the morning before snow gradually makes a transition to
a rain/snow mix and then potentially all rain. This should lead to a
slight improvement in ceilings and visibility, though confidence is
low on totally breaking out of IFR, especially at KJAC. KRKS is not
expected to see precipitation impacts. Gusty winds will be seen with
this system, especially in the afternoon. This will be most notable
at KJAC, which will first see strong southwest wind above the
surface before surface gusts reach 30 knots after 00Z Monday.

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

Precipitation will largely be confined west of the Divide. VFR
conditions are expected through tonight, with wind beginning to pick
up at KCPR by 16Z. KCOD and KLND will have the best chance of seeing
at least brief precipitation impacts coming off of the mountains
through the afternoon; KLND will carry a PROB30 group to account for
this potential. There is also the potential for strong winds at KLND
after 16Z as a mountain wave develops, though low confidence
precludes prevailing this wind for now. Wind shear at KLND is much
more certain during this period. KCPR is expected to see
southwesterly gusts to 40 knots after 00Z Monday.

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 Monday for WYZ001-002-012-
014-015-024.

&&

$$

DISCUSSION...LaVoie
AVIATION...Myers