A series of thunderstorms formed over western and central Wyoming during the morning and early afternoon hours. These storms eventually produced severe wind gusts at several locations.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS RIW wrote it up.
A series of thunderstorms formed over western and central Wyoming during the morning and early afternoon hours. These storms eventually produced severe wind gusts at several locations. The highest recorded gust was 71 mph at an automated observing site along Wyoming State Highway 120 near Meeteetse.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Riverton, WY wrote its last area forecast discussion before the first event at Sep 10, 2:12 AM MST, 6 hours 44 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 312 AM MDT MON SEP 10 2012 .SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT STRONG SOUTHWESTERLY FLOW ATOP AN INCREASING SURFACE PRESSURE GRADIENT WILL KEEP STRONG WINDS FLOWING AT THE SURFACE TODAY. A SURGE OF MID LEVEL MOISTURE WILL MOVE INTO SOUTHERN PORTIONS OF THE CWA...POSSIBLY REACHING INTO CENTRAL ZONES AS WELL. SURFACE BASED INSTABILITY WILL BE WEAK OVERALL BUT WITH HELP FROM THE RIGHT ENTRANCE REGION OF THE JET AND OROGRAPHIC LIFT A FEW HIGH BASED THUNDERSTORMS ARE EXPECTED ACROSS MUCH OF CENTRAL AND SOUTHERN WYOMING...WITH THE FOCUS SHIFTING FROM THE WEST EARLY ON...TO THE SOUTHEAST LATER IN THE EVENING AS AN UPPER LEVEL DISTURBANCE MOVES THROUGH. A RED FLAG WARNING FOR DRY THUNDERSTORMS WITH GUSTY OUTFLOW WINDS AND STRONG SURFACE WINDS WAS ISSUED FOR THESE ZONES. THE NORTHERN ZONES WILL REMAIN LARGELY DEVOID OF MOISTURE TODAY WITH STRONG WESTERLY WIND EXPECTED ACROSS THE REGION...A RED FLAG WARNING FOR STRONG WIND AND LOW HUMIDITY REMAINS FOR THESE ZONES. TUESDAY MAY ALSO SEE INCREASE FIRE BEHAVIOR AS A COLD FRONT MOVES THROUGH THE AREA. A SURGE OF MONSOONAL MOISTURE MAY GET INTO SOUTHERN WYOMING AHEAD OF THE FRONT...TO HELP GENERATE ADDITIONAL THUNDERSTORMS DURING THE AFTERNOON HOURS...BUT THE MOISTURE IS EXPECTED TO BE MORE ROBUST AT ALL LEVELS WITH THESE STORMS SO A RED FLAG WARNING IS NOT ANTICIPATED. OTHERWISE...THE COLD FRONT WILL RESULT IN A SHARP WIND SHIFT...WITH NEAR CRITICAL DRY AND GUSTY CONDITIONS TUESDAY AFTERNOON FOR WESTERN WYOMING. HOWEVER...IT WILL BE MUCH COOLER BEHIND THE FRONT WHICH MAY HELP TO COUNTERACT SOME OF THE EXTREME FIRE BEHAVIOR. WEDNESDAY WILL SEE A DRIER NORTHWEST FLOW DEVELOPING ACROSS THE AREA. PORTIONS OF WESTERN AND SOUTHERN WYOMING MAY EXPERIENCE INCREASED AFTERNOON WIND WITH LOWERING DAYTIME HUMIDITY. THIS MAY...AGAIN...BRING CRITICAL FIRE BEHAVIOR ACROSS WESTERN WYOMING. THE REMAINDER OF THE AREA IS EXPECTED TO HAVE LIGHT WIND THROUGH WEDNESDAY AFTERNOON. .LONG TERM...THURSDAY THROUGH MONDAY THURSDAY...CANADIAN HIGH PRESSURE SLIDES SOUTH ACROSS HIGH PLAINS BRINGING A MOSTLY CLEAR AND SEASONABLY COOL DAY. FRIDAY AND SATURDAY....WESTERLY FLOW BRINGS WARMER AND DRY WEATHER. SUNDAY AND MONDAY...CANADIAN COLD FRONT SLIDES SOUTH ACROSS AREA SUNDAY WITH COOL HIGH PRESSURE SETTLING OVER AREA MONDAY. SLIGHT CHANCE OF LIGHT RAIN AND HIGHER ELEVATION SNOW NORTHERN MOUNTAINS AND ACROSS INTERSTATE 25 CORRIDOR LATE SUNDAY. FORECAST WEIGHTED TOWARD GFS/GEFS THROUGH THIS PERIOD WITH ECMWF REMAINING AN OUTLIER DETACHING A CLOSED LOW FROM NORTHERN STREAM ACROSS THE NW U.S. INTO THE GREAT BASIN SUNDAY AND MONDAY. LARGE-SCALE CHANGES OCCUR DURING THIS PERIOD WITH UPPER HIGH OVER THE GREAT BASIN AND SOUTHWEST U.S. FLATTENING AND TILTING ACROSS WYOMING FRIDAY BEFORE REBUILDING WESTWARD ALONG 130W OVER THE WEEKEND. THIS WILL BRING A NW FLOW WITH NEXT ALBERTA CLIPPER DIVING INTO THE NORTHERN PLAINS ON SUNDAY. GFS TIMES ASSOCIATED CANADIAN COLD FRONT TO PUSH INTO NORTHERN WYOMING BY 18Z SUNDAY AND ACROSS I-80 BY 00Z MONDAY. IN COMPARISON TO WEDNESDAY/S FRONT...GFS PAINTS A VERY SIMILAR SCENARIO...LIMITED MOISTURE IN NW FLOW ALOFT WITH A SLIGHTLY MORE MODERATE VERTICAL TEMPERATURE PROFILE. FRIDAY AND SATURDAY WILL BE THE TWO DAYS WITH ELEVATED FIRE WEATHER CONCERNS...WARM TEMPERATURES...LOW RELATIVE HUMIDITY AND BREEZY CONDITIONS ACROSS THE SOUTH AND WEST IN THE AFTERNOON. && .AVIATION.../12Z ISSUANCE/ VFR CONDITIONS WILL PREVAIL ACROSS MUCH OF THE AREA THROUGH 12Z TUESDAY. A COLD FRONT WILL PUSH INTO NW WY AROUND 21Z AND THEN PUSH EAST AND SOUTH AFTER 00Z TUESDAY. THE FRONT WILL BE THROUGH THE REGION BY 12Z TUESDAY. BREEZY TO WINDY CONDITIONS WILL OCCUR TODAY AHEAD OF THIS FRONT. ISOLATED SHOWERS AND STORMS WILL DEVELOP AFTER 15Z ACROSS THE WEST AND SOUTHWEST. THIS ACTIVITY WILL MOVE EAST DURING THE MIDDAY AND AFTERNOON HOURS...DECREASING AFTER 00Z. LINGERING SHOWERS ARE POSSIBLE IN SOUTHERN WY UNTIL 06Z TUESDAY. AREAS OF SMOKE WILL OCCUR TODAY INTO TONIGHT DUE TO THE WILDFIRES IN PARTS OF WY. LOCAL MVFR CONDITIONS WILL OCCUR DUE TO THE LOWER VISIBILITY. && .FIRE WEATHER... CRITICAL FIRE WEATHER IS EXPECTED ACROSS THE STATE AGAIN TODAY AS STRONG SOUTHWESTERLY FLOW PERSISTS. SOME MID LEVEL MOISTURE WILL BRING SOME DRY THUNDERSTORMS IN THE AFTERNOON...AND INTO THE EARLY EVENING ACROSS CENTRAL AND SOUTHERN PORTIONS OF THE AREA. A COLD FRONT IS EXPECTED TO MOVE THROUGH THE AREA TONIGHT THROUGH TUESDAY MORNING. SOME MOISTURE MAY BE PRESENT ACROSS SOUTHERN WYOMING ALONG WITH THE FRONTAL PASSAGE TO BRING ANOTHER ROUND OF POTENTIALLY DRY THUNDERSTORMS ACROSS THE AREA...HOWEVER THE LOWER LEVELS LOOK LIKE THEY MAY RECOVER ENOUGH TO SUPPORT MORE WET THAN DRY STORMS ON TUESDAY. MODELS HAVE ALSO BEGUN TO HINT AT INCREASED AFTERNOON WIND ACROSS WESTERN WYOMING ON WEDNESDAY...WITH DRY CONDITIONS EXPECTED. ALL SCENARIOS WILL CONTINUE TO BE MONITORED. PLEASE CONTINUE TO CHECK OUR FIRE WEATHER PRODUCTS FOR THE MOST UP TO DATE INFORMATION. && .RIW WATCHES/WARNINGS/ADVISORIES... RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING WYZ140-277-279>281-283-285>289-300-414>416. RED FLAG WARNING FROM NOON TODAY TO 9 PM MDT THIS EVENING WYZ275-276-278-282. && SHORT TERM...ALLEN LONG TERM...AEM AVIATION...AR FIRE WEATHER...ALLEN
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 500 AM MDT MON SEP 10 2012 WYZ001>020-022>030-111100- ABSAROKA MOUNTAINS-BIGHORN MOUNTAINS SOUTHEAST- BIGHORN MOUNTAINS WEST-CASPER MOUNTAIN-CODY FOOTHILLS- EAST SWEETWATER COUNTY-FLAMING GORGE- GREEN MOUNTAINS AND RATTLESNAKE RANGE-JACKSON HOLE-LANDER FOOTHILLS- NATRONA COUNTY LOWER ELEVATIONS-NORTH BIG HORN BASIN- NORTHEAST JOHNSON COUNTY-OWL CREEK AND BRIDGER MOUNTAINS- ROCK SPRINGS AND GREEN RIVER-SALT RIVER AND WYOMING RANGES- SOUTH LINCOLN COUNTY-SOUTHEAST BIG HORN BASIN- SOUTHEAST JOHNSON COUNTY-SOUTHWEST BIG HORN BASIN-STAR VALLEY- TETON AND GROS VENTRE MOUNTAINS-UPPER GREEN RIVER BASIN- UPPER GREEN RIVER BASIN FOOTHILLS-UPPER WIND RIVER BASIN- WIND RIVER BASIN-WIND RIVER MOUNTAINS EAST-WIND RIVER MOUNTAINS WEST- YELLOWSTONE NATIONAL PARK- 500 AM MDT MON SEP 10 2012 ...RED FLAG WARNINGS FOR ALL AREAS THROUGH 9 PM THIS EVENING...BIG HORN BASIN MONDAY AFTERNOON AND EVENING... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT ISOLATED TO LOCALLY SCATTERED THUNDERSTORMS ARE EXPECTED WITH STORMS MOST NUMEROUS ACROSS THE SOUTHWEST. THE COMBINATION OF THE POTENTIAL FOR LIGHTNING TO IGNITE NEW FIRES ALONG WITH BREEZY TO WINDY CONDITIONS WILL RESULT IN CONTINUED CRITICAL FIRE WEATHER CONDITIONS ACROSS THE SOUTH AND WEST CENTRAL. CONTINUED VERY DRY...WARM AND BREEZY TO WINDY CONDITIONS WILL RESULT IN CRITICAL FIRE WEATHER CONDITIONS ACROSS THE NORTH CENTRAL AND EAST. PLEASE SEE RED FLAG WARNING PRODUCT FOR MORE INFORMATION. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY WEDNESDAY...VERY DRY AND GUSTY CONDITIONS WILL BRING ELEVATED FIRE WEATHER CONDITIONS ACROSS THE SOUTH IN THE AFTERNOON. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT. TEAM RIVERTON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 755 AM MDT MON SEP 10 2012 WYZ001-002-012-013-023-101530- ABSAROKA MOUNTAINS-JACKSON HOLE-STAR VALLEY- TETON AND GROS VENTRE MOUNTAINS-YELLOWSTONE NATIONAL PARK- 755 AM MDT MON SEP 10 2012 SHOWERS AND THUNDERSTORMS HAVE DEVELOPED OVER EASTERN IDAHO THIS MORNING AND ARE MOVING OVER PORTIONS OF YELLOWSTONE NATIONAL PARK... THE TETONS...THE ABSAROKAS...JACKSON VALLEY AND ALPINE. THE MAIN THREAT WITH THESE STORMS WILL BE LIGHTNING AND WIND GUSTS UP TO 35 MPH. THESE STORMS ARE MOVING OVER CRITICALLY DRY AREAS THAT HAVE HAD RECENT FIRE ACTIVITY. TL
The Riverton/Lander radar (KRIW), 138 km away, was scanning. The volume nearest the first event began at 15:54 UTC.
3 thunderstorm wind. Local standard time, as filed.
A strong thunderstorm moved east of the Absaroka Mountains and produced a severe wind gust at an automated observing site along State Highway 120 north of Meeteetse.
A strong thunderstorm moved off the Absaroka Range and produced a severe wind gust of 60 mph at the Grass Creek Divide RAWS site.
A strong thunderstorm brought a severe wind gust of 58 mph to the Pinedale Airport.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2012Every state in 2012This day in weather historyWarnings in Wyoming, September 2012
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 410038, 410047, 410051.