High Wind Warning 10, NWS Riverton, WY

Area Forecast Discussion
National Weather Service Riverton WY
430 AM MDT Wed Apr 22 2026

.KEY MESSAGES...

- A windy day is expected today with widespread 30 to 55 mph
  southwesterly wind gusts. Wind prone locations could see wind
  gusts above 60 mph (50-80%).

- A Red Flag Warning is in effect for all areas east of the
  Divide today. Should a fire start, rapid fire spread and
  erratic fire behavior is expected due to the strong winds.

- Western mountain snow and western valley rain and snow is
  forecast to begin late this morning and continue through late
  Thursday. Winter travel conditions are expected across all
  western mountain passes due to snow and wind.

- A cooler, more active weather pattern is favored Friday
  through the upcoming weekend.

&&

.DISCUSSION...
Issued at 323 AM MDT Wed Apr 22 2026

Satellite water vapor imagery at 09Z/3AM shows an upper level low
circulating over northern California/Nevada with southwesterly flow
over Wyoming. An associated surface low is located over
northeast Idaho with a cold front over western Utah. This system
will be our "weather maker" as it ejects into Montana today,
bringing critical fire weather conditions, widespread wind, and
precipitation chances.

The pressure and temperature gradient will tighten through the day
today as the cold front approaches from the west. Additionally, an
80kt to 100kt upper level jet will be present across the Wind
Corridor as the low shifts into Montana. This will result in
widespread strong and gusty southwest winds a majority of the day.
Southwest winds will quickly ramp up between 9AM and 10AM this
morning as deep mixing begins. Widespread wind gusts of 30 to 50 mph
can be expected (90%+ chance) across most low elevations. Wind prone
locations could see occasional gusts of 60 mph or greater,
especially in the hour or two ahead of the frontal passage. There
are some indications of a mountain wave breaking over the eastern
slopes of the Wind River Mountains in the morning to early afternoon
hours. Should this occur, wind gusts of 50 to 70 mph are possible
across the eastern slopes of the Wind River Mountains and
potentially making it around Lander and Fort Washakie. The cold
front is forecast to traverse the state between 2PM and 6PM today,
with wind gusts remaining in the 30 to 40 mph range for a few hours
behind the front due to the temperature gradient.

The strong and gusty winds mentioned above in combination with dry
air ahead of the cold front will create critical fire weather
conditions for all areas east of the Divide. Minimum relative
humidity values are forecast to be in the 10 to 13 percent range
this afternoon. A Red Flag Warning is now in effect from 9AM to 8PM
today. Behind the cold front, relative humidities are forecast to
increase to a 15 to 25 percent range through sunset. The expected
strong winds behind the front will keep conditions favorable for
erratic fire behavior despite minimum relative humidities likely
being above Red Flag Criteria (15 percent or less) from 5PM to 8PM.

The final component of this weather system will be the precipitation
chances along and behind the cold front. Because of the Pacific
origin of the system, there will enough available moisture to bring
accumulating mountain snow and low elevation rain and snow to the
west. Through late Thursday night, there is an 80 to 95 percent
chance of at least 8 inches of snow for elevations above 7,500 feet
across the western mountains. Chances of 12 inches or more are in
the 40 to 70 percent range and confined to the Tetons. Gusty winds
of 30 to 50 mph will also be common. Given the slightly lower
confidence in widespread 12 inches or more of snow and the higher
sun angle, opted to maintain the Winter Weather Advisory. The
Absaroka Mountains have been added to the Winter Weather Advisory
with an 80 to 90 percent chance of snow accumulations of 6 inches or
more and gusty 50 to 70 mph winds. Winter travel conditions are
expected with the snow and gusty winds across all western mountain
passes. There will also be enough instability (up to 500 J/kg of
CAPE) to support some instances of thundersnow. As for Jackson
Valley and Star Valley, precipitation will remain as rain most of
the daylight hours today before changing over to snow after sunset
when snow levels drop below 6,000 feet.

Precipitation will largely be focused across the west today through
at least mid-day Thursday due to the low passing north of Wyoming.
On Thursday afternoon, a shortwave is forecast to drop down from
Canada and provide support for another front to traverse the state.
This front is forecast to bring cooler temperatures and
precipitation. Precipitation will finally push east of the Divide
late Thursday through most of Friday, first as rain across low
elevations. Rain will quickly change over to snow overnight Thursday
into Friday with 700 mb temperatures behind the front being in the
minus 6 Celsius to minus 10 Celsius range. However, snow amounts are
forecast to be minimal by Friday night with less than a 40 percent
chance of 2 inches of snow for the basins.

By Saturday, the above normal temperatures that we have been
experiencing will be a thing of the past. Lower 500mb heights are
forecast across Wyoming Saturday as the previously mentioned upper
level low sits itself over southern Canada. By late Saturday,
ensemble guidance is in consensus that an associated longwave trough
will develop over the western CONUS with embedded passing
shortwaves. There are also indications that upper level troughing
and embedded shortwaves, will keep an almost constant fetch of
moisture into the Northern Rockies. If this comes to fruition, a
more active period of more widespread precipitation is favored late
Saturday into early next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 430 AM MDT Wed Apr 22 2026

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

VFR conditions to start the period as winds increase starting
after around 15Z. Highest winds during peak heating of the
afternoon ahead of FROPA, up to 30kts at JAC, 35kts at BPI/PNA,
and up to 40kts at RKS. These winds will slowly diminish some
but remain elevated after sunset around 03Z, highest at RKS but
down to around 10-15kts at all other locations after 10-11Z.
Shower activity increases around 18-19Z at all but RKS due to
the shortwave more north not affecting further south.
Thunderstorm chances with enough instability during the
afternoon with PROB30 groups diminishing after 04Z outside of
JAC even through the overnight hours. The next round will be
into the next TAF cycle for Thursday afternoon. MVFR conditions
may exist with storm/shower activity on station with mountain
obscuration evident for much of the afternoon/evening
timeframe.

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

VFR conditions with no precipitation expected until the next
TAF cycle for Thursday afternoon. The main threat will be wind
increasing after 16Z ahead of FROPA. Highest wind speeds at
CPR/RIW up to 40kts, 35kts at COD/LND/WRL. These winds will
diminish some after 03Z about 10-15kts less than the peak
heating of the afternoon. Mountain obscuration likely for the
Winds/ Absarokas with the winter weather west of the Divide but
increasing in coverage going into the next TAF cycle for
Thursday afternoon and beyond.

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

&&

.FIRE WEATHER...
Issued at 323 AM MDT Wed Apr 22 2026

Warm, dry, and windy weather will cause critical fire weather
conditions east of the Divide today ahead of an approaching cold
front. East of the Divide and ahead of the cold front, relative
humidity values are forecast to be in the 10 to 15 percent range
with widespread southwesterly gusts of 35 to 55 mph. Occasional
gusts of 60 mph or greater are possible, especially for wind prone
locations. The cold front is forecast to trek across the area between
2PM and 6PM today, with relative humidity to be in the 15 to 25
percent range behind the front. Winds will remain gusty through
sunset. Elevated fire weather conditions are expected across
southern Wyoming today as well. Should a fire start, especially
ahead of the cold front, erratic fire behavior and rapid fire
spread is expected.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from noon today to 11 PM MDT Thursday
for WYZ001-002-012-024.

Red Flag Warning from 9 AM this morning to 8 PM MDT this
evening for WYZ275-276-280>283-285-287-289-300.

&&

DISCUSSION...Gerhardt
AVIATION...Lowe
FIRE WEATHER...Gerhardt

Hazardous Weather Outlook
National Weather Service Riverton WY
336 AM MDT Wed Apr 22 2026

WYZ001>020-022>030-231345-
Yellowstone National Park-Absaroka Mountains-Cody Foothills-
North Bighorn Basin-Southwest Bighorn Basin-Southeast Bighorn Basin-
Owl Creek and Bridger Mountains-Bighorn Mountains West-
Bighorn Mountains Southeast-Northeast Johnson County-
Southeast Johnson County-Teton and Gros Ventre Mountains-
Jackson Hole-Wind River Mountains West-Wind River Mountains East-
Upper Wind River Basin-Wind River Basin-Lander Foothills-
Green Mountains and Rattlesnake Range-
Natrona County Lower Elevations-Casper Mountain-Star Valley-
Salt River and Wyoming Ranges-Upper Green River Basin Foothills-
Upper Green River Basin-South Lincoln County-
Rock Springs and Green River-Flaming Gorge-East Sweetwater County-
336 AM MDT Wed Apr 22 2026

...WINTER WEATHER ADVISORY IN EFFECT FROM NOON TODAY TO 11 PM MDT
THURSDAY FOR THE TETON AND GROS VENTRE MOUNTAINS, THE SALT RIVER AND
WYOMING RANGES, THE ABSAROKA MOUNTAINS, AND YELLOWSTONE NATIONAL
PARK...
...A RED FLAG WARNING IS IN EFFECT FROM 9 AM TO 8 PM MDT
TODAY FOR ALL AREAS EAST OF THE CONTINENTAL DIVIDE...

This Hazardous Weather Outlook is for Western and Central Wyoming.

.DAY ONE...Today and tonight.

Strong 30 to 55 mph winds and low humidity will create critical fire
weather conditions for all areas east of the Continental Divide.
Wind prone locations could see wind gusts of 60 mph or greater.

Western mountain snow and wind will lead to winter travel conditions
across the western mountain passes beginning late this morning.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Thursday through Friday...Western mountain snow will lead to winter
travel conditions across the western mountain passes.

Sunday through Monday... Widespread rain and/or snow chances.
However, accumulations look to be minimal at this time.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to Standard Operating Procedures.