793
FXUS65 KRIW 101754
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1154 AM MDT Thu Sep 10 2026

.KEY MESSAGES...

- Warm, dry, and windy conditions with mostly clear skies
  continue Thursday. Afternoon high temperatures will be 5 to 10
  degrees above normal east of the divide, and 3 to 6 degrees
  above normal west of the divide.

- Elevated to critical fire weather conditions persist today due
  to gusty afternoon west to northwest wind 20 to 30 mph and
  minimum relative humidity in the single digits to middle
  teens.

- Clouds will increase from west to east this afternoon with a
  slight chance of virga showers Thursday evening through
  Friday morning.

- The timing for the weekend storm system has been pushed to
  Sunday, meaning that Saturday will now be partly cloudy with a
  minimal chance for precipitation, warmer temps in the low 80s
  (except across northern WY), and breezy WSW winds.

- Precipitation chances have also been pushed to northern
  portions of Wyoming, as the track of the storm stays to the
  north. The cold front looks to move through Sunday night,
  leading to freezing temperatures across western portions of
  the state again, with cooler days on Monday and Tuesday.

&&

.UPDATE...
Issued at 1155 AM MDT Thu Sep 10 2026

Skies are mostly clear late this morning across western and
central Wyoming, with west-southwest winds increasing from
southwest into central WY, and along the east slopes of the
mountain ranges. Conditions are stiff favorable (wind and
humidity) for fire weather conditions across much of the area
this afternoon and early evening, especially with high temperatures
in the mid to upper 80s east of the divide. High clouds will
move into western WY between noon and 2 PM from the west-
southwest, moving eastward. Moisture will increase in the mid-
levels overnight, creating scattered virga and light
precipitation showers across central and southern WY from about
midnight through noon Friday. The cloud cover will keep
overnight low temperatures warmer than what has been felt the
last couple of mornings. As this area of cloudiness moves
eastward Friday afternoon, west-southwest winds will again
increase across western and south-central WY, but humidity
values will not be as dry as this afternoon. At the same time
late afternoon Friday, a cool front is expected to push into
northern WY from Montana, bringing cooler temps and gusty north
winds into the Bighorn Basin and Johnson County. A stationary
boundary/front then sets up just east of the continental divide
as stronger southwest flow sets up for Saturday. With the
slowing of the large scale trough over the Pacific Northwest,
Saturday should be warmer than previously expected, expect for
far northern WY. Sunday looks to be the more active day as the
upper-level low center move from central ID into central MT and
brings a tightened pressure gradient through WY. Unfortunately,
precipitation chances are decreased for much of WY, with the NW
WY mountains having the better chances for showers.

&&

.DISCUSSION...
Issued at 200 AM MDT Thu Sep 10 2026

Another day of critical fire weather conditions returns across the
CWA today. RH values ranging between 7 to 15 percent will occur for
most lower elevation locations this afternoon. Model forecasts for
wind gusts have trended slightly downward for this afternoon. Winds
will steadily increase through the afternoon, with gusts of 25 to 30
mph occurring over western portions of the forecast area and from
the southwestern corner of the state to Natrona County. The higher
gusts of 35 mph will be more confined to the eastern slopes of the
Absaroka and Wind River Mountains. Burning of any kind continues to
be highly discouraged! Otherwise, today will also be the warmest day
of the week, with highs in the middle to upper 80s east of the
Divide. Readings in the middle to upper 70s will occur west of the
Divide.

Clouds will begin to increase from west to east through the
afternoon. This will gradually lead to a chance for virga showers
this evening into Friday morning. The central basins look to have
the best chances between 01Z and 06Z with the main impact being
gusty outflow winds. Winds will stay elevated for most areas and
begin to decrease after 03Z Friday (9pm Thursday), with gusts up to
35 mph continuing over the east slopes of the Absaroka and Wind
River Mountains through the rest of the night. Isolated virga
showers will become possible over western portions by 12Z Friday
morning and end by 18Z. These showers will be part of a larger push
of moisture from UT/ID moving over the Cowboy State. This influx of
moisture will also be the cause why humidity values will not drop
below the critical threshold Friday afternoon.

The timing for the cold front has been pushed toward late afternoon,
moving through Jackson, Cody and Kaycee by 00Z Saturday (6pm
Friday). Temperatures will be slightly cooler east of the Divide as
a result, especially for northern portions of the CWA. Widespread
wind gusts of 30 to 35 mph remain in the forecast for Friday,
keeping fire weather conditions elevated. The front will make it to
the Divide by 06Z Saturday, becoming stationary through the rest of
the night into Saturday morning.

The forecast for the weekend storm system has shifted dramatically
this run. The storm system will drop southward along the West Coast
Friday night into Saturday, a track that is much further west than
previous runs. This will cause the aforementioned cold front to
retreat northward Saturday afternoon, due to an increase in
southwesterly winds. Initial indications show the front getting
pushed into the Bighorn Basin and Johnson County by Saturday
evening. Conditions are expected to remain dry until Sunday morning,
as the storm begins to track over the Northern Rockies.
Precipitation looks to stay confined over northern portions through
the day Sunday as the storm stays further north in MT. The associated
cold front will push through the Cowboy state Sunday night, clearing
the forecast area by 12Z Monday. Sub-freezing temperatures will
return to western portions, with readings in the upper 30s to lower
40s elsewhere. Dry and cooler conditions will be in place Monday,
with highs in the 60s to near 70 degrees across the area. Another
cold front looks to clip northern portions on Wednesday.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1122 AM MDT Thu Sep 10 2026

Westerly zonal flow prevails across the forecast area through
midday Friday. A batch of cloudiness and embedded showers across
the northern Great Basin will track to the western border by
Thursday evening and traverse the region overnight. There is a
slight chance of light showers at KJAC and perhaps KBPI and KPNA
between about 09Z-13Z/Friday, but have not placed PROB30 in any
forecast at this time. Much of the increased mid-level cloud
deck will lead to virga showers overnight and Friday morning.
Westerly surface wind continues to increase at most terminals by
20Z/Thursday. KRIW and KLND should again see a favorable west-
northwest wind 10-20kts toward 00Z/Friday which lingers into
the evening hours, while KWRL stays less than 10kts. Other
terminals see winds decrease by 03Z/Friday. The gusty westerly
wind increases at many terminals between 15Z-18Z/Friday ahead of
an approaching afternoon cold front from the north. Occasional
mountain top obscurations between 07Z-15Z/Friday.

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

&&

.FIRE WEATHER...
Issued at 200 AM MDT Thu Sep 10 2026

Winds have trended downward slightly for this afternoon and will
gradually increase through the afternoon. Wind gusts of 25 to 30
mph are now expected, with higher gusts of 35 mph expected in
zones 286 and 288. Critical RH values between 7 and 15 percent
will occur in most lower elevation zones this afternoon.

Clouds will increase from west to east through the afternoon.
Virga showers will be possible in the Wind River and Bighorn
Basins between 1800 and 2300. Wind gusts around 25 mph will be
possible from any outflow boundary. RH recovery will be fair to
poor once again tonight for zones east of the Divide.

Virga showers will be possible over western portions Friday
morning. This increase in moisture will keep RH values from
dropping to critical thresholds, ranging between 17 and 25
percent. A cold front will drop southward late in the afternoon
reaching the Divide Fright night.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM MDT this evening for WYZ286>288.

Red Flag Warning until 9 PM MDT this evening for WYZ277>280-
289-300.

&&

$$

UPDATE...McDonald
DISCUSSION...LaVoie
AVIATION...CNJ
FIRE WEATHER...LaVoie