Mills, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

604
FXUS65 KRIW 230040
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
540 PM MST Sun Feb 22 2026

.KEY MESSAGES...

- High temperatures climb to 10 to 15 degrees above normal
  Monday as warmer air arrives. Similar daytime highs occur
  through the work week.

- Mountain snow is forecast across western Wyoming Tuesday and
  Wednesday, with the heaviest snowfall rates between 5 AM
  Tuesday and 5 AM Wednesday. Mountains within the Winter Storm
  Watch have a 70 percent chance of one foot or more of snow.

- Western Wyoming valleys will receive precipitation Tuesday,
  but with surface air temperatures near freezing, there is low
  confidence in snow levels. Places like Jackson Hole and Star
  Valley could (40 percent chance) receive notable snowfall with
  this event if temperatures remain slightly cooler than
  currently forecast.

- There will be a prolonged period of very windy conditions
  along and east of the Continental Divide beginning Monday
  night and lasting through Friday. Wednesday appears to be the
  windiest day of the week with widespread 35 to 45 mph wind
  gusts, and lower elevations of central Wyoming topping 50
  mph.

&&

.UPDATE...
Issued at 102 PM MST Sun Feb 22 2026

The incoming warmer, moist, strong, zonal flow beginning late
Monday night and continuing into Wednesday morning has led to
the issuance of a mix of winter storm watches and high wind
watches across the western mountains. The warmer air leads to
high temperatures 10 to 15 degrees above normal Monday, a trend
that persists through the week for all but the far west valleys
and high deserts.

The leading edge of an atmospheric river (IVT 300-400 kg/ms) reaches
the western mountains just prior to 5 AM Tuesday. Favorable
isentropic lift combined with orographics leads to a prolonged
period of snowfall from southern Yellowstone to the north half of
the Salt River/Wyoming Ranges. The heaviest snow falls between 8 AM
Tuesday and 5 AM Wednesday and favors the Teton Range, Pitchstone
Plateau, and the area around and north of Togwotee Pass. There is a
70 to nearly 100 percent chance of one foot or more of snow in these
areas, which necessitated the issuance of winter storm watches.
There is close to a 50 percent chance of totals exceeding 18 inches
in the Teton Range. This airmass is moist, so this looks possible.
The challenge remains regarding valley rain/snow as warm air
advection could lead to warmer daytime highs, in turn hindering
valley accumulations.

Wind along and east of the Continental Divide will be the other
aspect to this incoming event. The initial surge of stronger wind
arrives late Monday night and Tuesday across the Absaroka Range and
portions of the Cody Foothills. This surge shifts south to the Wind
River Range, including Red Canyon, and the Upper Wind River Valley
around Dubois during the day. A high wind watch has been posted for
these areas, but confidence is marginal. A more westerly component
to the wind may hinder wind gust potential in the Lander Foothills,
so have kept that zone out of the watch for now. The more widespread
wind event arrives Wednesday as a 130kt+ jet and elongated vorticity
axis shift south across Wyoming. The chance of widespread 50+ mph
wind gusts Wednesday is 30 to 50 percent east of a Cody to Dubois
to Rock Springs line. We decided to message this strongly, and
wait for a later shift to make a determination on upgrading the
first set of high wind watches before creating a second set of
watches. Nonetheless, Wednesday will be very windy across a
substantial area.

&&

.DISCUSSION...
Issued at 231 AM MST Sun Feb 22 2026

Today will likely be the calmest day of the week. Temperatures will
be 5 to 10 degrees warmer today, rebounding back to near normal
levels. Conditions will remain dry, with high clouds this morning
giving way to clear skies by the afternoon. Winds will be light for
most locations. Exceptions will be the east slopes of the Absaroka,
Wind River and Bighorn Mountains and the Wind Corridor east of the
Divide (Muddy Gap/Jeffrey City to Casper). Gusts of 25 to 30 mph
will occur in these areas. Similar conditions return for Monday,
with temperatures 10 to 20 degrees warmer across the area leading to
highs in the 45F to 55F range. Gusty winds will impact the
previously mentioned areas again, with higher gusts of 35 to 55 mph
occurring through the afternoon. Wind gusts of 25 to 35 mph will be
more widespread as well, from southern Lincoln County to southern
Johnson County. These increased winds will be due to the pressure
gradient tightening associated with an approaching storm system
that will begin to impact western portions later Monday night.

An atmospheric river (AR) will develop over the PACNW tonight into
Monday, as a broad ridge develops over much of the Intermountain
West Monday night into Tuesday. This pattern will lead to the core
of the PFJ being over the PACNW and Canadian border. At the same
time, Pacific moisture from this AR will begin to increase over the
region, with the first rounds of snow developing over the western
mountains late Monday night. Precipitable water (PWAT) values will
rapidly increase between 06Z and 12Z Tuesday, with values of 0.35"
to 0.4" becoming widespread across the Cowboy State. This is well
above the 90th percentile and toward the climatological maximum.
This, coupled with strong isentropic upslope, will lead to heavy
snow. There remains a high probability (greater than 70 percent) of
widespread snowfall of at least 8 inches over the northwestern
mountains (including Yellowstone), while the Tetons and southern
Absarokas have a 40-60 percent chance of totals over 15 inches. The
chances for snow in the Jackson and Star Valleys are highly
variable, as model solutions are waffling on snow levels (which are
currently between 6000 and 7000ft). This is likely due to the
Pacific nature of the airmass. However, there is up to a 50% chance
for 2 inches or more in the Jackson Valley (with higher chances on
the north end of the valley between Moose and Moran) and a 10 to 20%
chance in Star Valley through the day Tuesday and into Tuesday
night.

Gusty winds will also continue over the mountains and increase late
Monday night as well, as the gradient continues to tighten as a
system begins to drop southward from Canada. 700mb winds will
increase to 50 to 70kt between 09Z and 12Z Tuesday, with a strong
downsloping signature off the east slopes of the Absaroka and Wind
River Mountains occurring by 12Z. This could lead to high winds
(wind gusts 60+ mph) at places like Cody, Dubois and Lander.
Needless to say, gusty winds will be more widespread with gusts of
35 to 50 mph occurring from southern Lincoln County to Natrona
County Tuesday afternoon. Locally higher gusts around 60 mph will
occur over South Pass. Caution is advised for travelers here, as
well as over Togwotee/Teton Pass, with gusts of 25 to 35 mph
occurring with the snow.

The aforementioned Canadian system will rapidly drop southward
across the forecast area through the day Wednesday. Strong to high
winds will be widespread across the CWA as a result. The main reason
will be due to a 130kt jet max associated with the PFJ that will be
in place ahead of the system. This will translate to 700mb winds of
45 to 60kt, which will mix down to the surface. Most areas can
expect wind gusts of 40 to 60 mph through the day on Wednesday.
These winds will decrease for most areas after sunset Wednesday
evening, but gusts of 25 to 40 mph will continue for wind prone
locations. Moderate to heavy snow will also continue over the
western mountains Wednesday, ending by the evening as well, as the
main system exits to the south.

Strong gusty winds will continue across the area Thursday in the
wake of the storm, as northwest winds persist. Another Canadian
storm system could impact the area with cold temperatures and snow
by Saturday. Most of the impacts will likely stay east of the Divide
if current trends continue.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 403 PM MST Sun Feb 22 2026

VFR conditions through the period. Winds increase starting Monday
morning ahead of the next weather system. At KCOD, wind shear due to
westerly 35 to 50 knot winds are possible as winds aloft come off
the Absaroka Mountains. For most locations, gusty winds are expected
for sites late morning and through the afternoon.

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 Watch from late Monday night through Wednesday
morning for WYZ001-002-012-024.

High Wind Watch from Monday evening through Tuesday afternoon
for WYZ002-003-015-016.

&&

$$

UPDATE...CNJ
DISCUSSION...LaVoie
AVIATION...Wittmann