099
FXUS65 KRIW 082157
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
357 PM MDT Tue Sep 8 2026

.KEY MESSAGES...

- Elevated to critical fire weather conditions this week due to
  gusty winds 25 to 40 mph and low humidities under 20 percent.

- Freezing temperatures expected across western valleys and
  basins Wednesday morning. Sensitive outdoor plants could be
  affected by freeze and frost.

- Temperatures remain near seasonal normals through the week,
  with minimal chances for rain.

- Confidence continues to increase for a storm system this
  weekend, which would bring colder temperatures.

&&

.UPDATE...
Issued at 1153 AM MDT Tue Sep 8 2026

The main changes with this update are the addition of Freeze
Warnings and Fire Weather Watches, as it is that time of year where
the duality of fire and ice exists in Wyoming. Starting with the
freezes, temperatures over the western Wyoming valleys and basins
are again expected to drop below freezing (32 degrees F) tonight.
Many places this morning saw mid-20s to mid-30s. With little change
in the forecast compared to last night, another night of widespread
freezes are expected. Impacted locations include the Green River
Basin, Jackson and Star Valleys, and the lower elevations of Lincoln
County. Sensitive plants will likely see frost or freezes tonight
into Wednesday morning.

Fire Weather Watches have also been issued for fire zones 277, 278,
and 279 for Wednesday afternoon and evening, which includes the
Green River Basin, Sweetwater County, southern Lincoln County, and
Uinta County. Minimum humidity will be under 15 percent for these
areas, with afternoon winds around 25 mph. Red Flag Warnings
continue to be in effect for portions of central Wyoming.

&&

.DISCUSSION...
Issued at 210 AM MDT Tue Sep 8 2026

Clear skies are in place across the CWA this morning and will be
the norm for the next few days. This will help temperatures to
drop this morning, in addition to the cooler airmass in place
in the wake of yesterday`s cold front. Freezing temperatures
will be possible in the more cold-prone locations west of the
Divide, like Jackson, Pinedale and Hoback Junction. Dewpoints
are around 27 degrees as of 07Z (1am), with nearly calm winds so
would not be surprised if temperatures drop below freezing in
these areas. Dewpoints are slightly higher in Star Valley,
around 32 to 34 degrees at Afton and Alpine so temperatures look
to stay just above freezing.

The trend this week will be the dry conditions along with breezy
winds, along with seasonal temperatures and mainly clear skies.
Red Flag Warnings are in effect again today across areas east
of the Divide, from the Cody Foothills to the Wind River Basin
and over Natrona County. West winds, with gusts of 25 to 35 mph,
will be widespread across much of the CWA again this afternoon.
Eastern portions of the Bighorn Basin and most of Johnson County
will be the exceptions. A second cold front will reach northern
portions around 00Z and quickly push southward through the
evening hours. The front will be dry, as there is no available
moisture in place after yesterday`s cold front.

Wednesday will be the calmest day of the week. Seasonal
temperatures will remain in place and the winds will not be as
strong as today or yesterday. West winds with gusts up to 30 mph
will be mainly confined to more wind prone locations, mainly
from southern Lincoln County to Natrona County. Red Flag
Warnings will be likely in these areas, as critically low RH
values become widespread. Stronger winds return for Thursday,
with widespread gusts of 30 to 40 mph occurring for most areas.
Daytime temperatures will also be slightly above normal for
areas east of the Divide. Another cold front will move over the
area Friday, causing another day of gusty winds of 30 to 40 mph
impacting much of the CWA.

Models continue to trend toward a strong cold front impacting
the Cowboy State this weekend and have come more inline wrt
timing. Confidence is medium for widespread precipitation ahead
of the system on Saturday. If there is any snow with this storm,
it would be confined to the northwestern mountains and the
northern end of the Bighorns Sunday night into Monday morning.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 355 PM MDT Tue Sep 8 2026

VFR conditions prevail over the next 24 hours. Breezy winds
have been slow to mix down to the surface this afternoon, but
weather models continue to show a couple hours of breezy winds
before sunset, even for sites east of the Continental Divide.

After sunset, winds will quickly diminish. Winds will be light
and variable overnight, and not as breezy on Wednesday
afternoon. No fog or precipitation expected.


&&

.FIRE WEATHER...
Issued at 210 AM MDT Mon Sep 7 2026

West winds with gusts of at least 25 mph and critically low RH
values will occur in various locations today through Thursday.
Red Flag Warnings are in effect this afternoon for areas east of
the Divide. Winds will shift to southern portions of the state
Wednesday, as critical RHs become widespread. Thursday will have
the strongest winds, with gusts of 30 to 40 mph occurring in
most zones. Another cold front will move through the area
Friday, but RH values are expected to range between 16 and 25
percent.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 7 PM MDT this evening for WYZ276-283-
285-287.

Freeze Warning from 2 AM to 9 AM MDT Wednesday for WYZ013-023-
025>027.

Fire Weather Watch from Wednesday afternoon through Wednesday
evening for WYZ277>279.

Red Flag Warning until 9 PM MDT Thursday for WYZ280-289-300.

&&

$$

UPDATE...Wittmann
DISCUSSION...LaVoie
AVIATION...VandenBoogart
FIRE WEATHER...LaVoie