A thunderstorm moved into the Star Valley producing outflow wind gusts that caused damage in the town of Freedom.
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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 thunderstorm moved into the Star Valley producing outflow wind gusts that caused damage in the town of Freedom.
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 Oct 1, 11:08 AM MST, 3 hours 1 minute earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 1208 PM MDT SAT OCT 1 2011 .SHORT TERM...TODAY THROUGH MONDAY NIGHT THE MONSOON HAS RETURNED TO THE INTERMOUNTAIN WEST AS A FOUR CORNERS HIGH BRINGS IN SUBTROPICAL MOISTURE. SHOWERS AND THUNDERSTORMS IN UTAH FRIDAY AFTERNOON INDICATE THE MOISTURE WILL BE FULLY OVER WESTERN WYOMING IN TIME FOR AFTERNOON HEATING TO TOUCH OFF SOME ISOLATED CONVECTION TODAY. H7 TEMPS UNDER HIGH PRESSURE WILL BE IN THE 10-12C RANGE TODAY BRINGING NEAR RECORD HIGHS TO MUCH OF THE LOWER ELEVATIONS EAST OF THE CONTINENTAL DIVIDE. SOME RECORDS ARE LIKELY TO FALL PARTICULARLY IN THE BIG HORN BASIN AND IN THE LOWER ELEVATIONS OF JOHNSON AND NATRONA COUNTIES. WHILE FIRE WEATHER DANGER WILL BE HEIGHTENED BY THE HOT TEMPERATURES BRINGING LOW HUMIDITY EAST OF THE DIVIDE...WIND IS EXPECTED TO REMAIN BELOW RED FLAG CRITERIA EXCEPT POSSIBLY IN ISOLATED FAVORED AREAS. ISOLATED SHOWERS WILL DEVELOP THIS AFTERNOON ACROSS MUCH OF WESTERN WYOMING WITH MAX DAYTIME HEATING. MARGINAL INSTABILITY WITH LI VALUES AROUND ZERO AND MID LEVEL LAPSE RATES OF 8 TO 8.5 C/KM INDICATES THE POTENTIAL FOR A FEW THUNDERSTORMS TO FORM AS WELL. SUNDAY WILL SEE AN INCREASE IN MOISTURE THAT WILL BRING INCREASED COVERAGE OF PM CONVECTION IN THE WEST AND SOUTH. INSTABILITY PARAMETERS SEEM A BIT LESS FAVORABLE SUNDAY BUT A RUMBLE OF THUNDER OR TWO IS STILL POSSIBLE. WITH INCREASED COULD COVER AND A SLOW TRANSLATION EASTWARD OF THE RIDGE...HIGHS ON SUNDAY WILL BE A FEW DEGREES COOLER BUT STILL WELL ABOVE NORMAL FOR THE START OF OCTOBER. A SIMILAR DAY IS EXPECTED MONDAY WITH SHOWERS IN THE WEST AS A PACIFIC SYSTEM BEGINS TO MAKE ITS WAY ASHORE. THIS NEXT SYSTEM WILL BE A BIG PLAYER LATER IN THE WEEK. .LONG TERM...TUESDAY THROUGH SATURDAY TUESDAY WILL FEATURE SW FLOW ALOFT WITH A CHANCE OF AFTERNOON AND NIGHT SHOWERS IN THE WEST AND SOUTHWEST. ISOLATED THUNDERSTORMS CANNOT BE RULED OUT. DRY WEATHER ELSEWHERE. MAJOR TROUGH OF LOW PRESSURE DIGS INTO THE WESTERN U.S. ON WEDNESDAY WITH A SOUTH TO SOUTHWEST FLOW ALOFT OVER THE AREA. AGAIN THE BEST CHANCE OF SHOWERS AND A FEW STORMS WILL BE OVER THE WEST AND SOUTHWEST. WILL KEEP THE REST OF THE REGION DRY. AGAIN BIG DIFFERENCES IN THE LONG RANGE MODELS THURSDAY THROUGH SATURDAY WITH THE EVOLUTION OF THE TROUGH OVER THE ROCKY MOUNTAIN STATES. GFS CONTINUES TO BE THE FASTEST AND PROGRESSIVE WITH THE LACK OF A STRONG CLOSED CIRCULATION. IT WOULD BRING RAIN AND SNOW THURSDAY AND FRIDAY WITH AN UNSETTLED NW FLOW ALOFT ON SATURDAY FOR LINGERING SHOWERS. THE ECMWF HAS WENT BACK TO ITS UPPER LOW SCENARIO OVER THE SW U.S. THURSDAY AND THEN MOVES IT TO THE FOUR CORNERS FRIDAY AND CUTS IT OFF FROM THE FLOW PATTERN ON SATURDAY. THE CANADIAN HAS A DEEP CIRCULATION OVER THE SW U.S. THURSDAY THEN MOVES THE STORM TO NORTHEAST UTAH FRIDAY AND ACROSS WY SATURDAY. A FEW GFSENSEMBLE MEMBERS HINT AT AN UPPER LOW OVER THE SW U.S. THURSDAY AND THEN TOWARD THE FOUR CORNERS AREA ON FRIDAY. THE UNCERTAINTY RUNS HIGH WITH WHICH DAYS WILL BE THE WETTEST AND COLDEST. FOR NOW HAVE KEPT WITH FRIDAY BEING RATHER COLD AND WET AND THIS MAY LAST INTO SATURDAY. UNTIL THEN TUESDAY AND WEDNESDAY WILL BE MILD WITH THE START OF COOLER HIGHS ON THURSDAY. && .AVIATION.../18Z ISSUANCE/ SOME MONSOONAL MOISTURE WILL CONTINUE TO PUSH NORTHWARD THIS AFTERNOON WHICH SHOULD RESULT IN ISOLATED CONVECTION ACROSS THE SOUTHWEST AND WESTERN WYOMING THIS AFTERNOON. WILL HAVE CB IN WESTERN AND SOUTHERN TAF SITES TO ACCOUNT FOR THIS ACTIVITY. SOME WEAK CONVECTION HAS ALREADY BROKEN OUT OVER THE UINTA MOUNTAINS AND HAVE SPREAD NORTH INTO FAR SOUTHWEST SWEETWATER COUNTY. EXCEPT NEAR CONVECTION AND THE SMOKE FROM WILDFIRES ACROSS THE WEST...VFR CONDITIONS WILL PREVAIL THROUGH TONIGHT. DUE TO THE INVERTED V SOUNDINGS...VERY GUSTY WINDS WILL BE THE MAIN HAZARD WITH THE CONVECTION TODAY. OTHERWISE WINDS WILL GENERALLY BE LIGHT...EXPECT 10-15 KTS FROM THE WEST/SOUTHWEST ACROSS THE WIND CORRIDOR. && .FIRE WEATHER... HOT AND DRY CONDITIONS ARE ON TAP FOR THE LOWER ELEVATIONS EAST OF THE CONTINENTAL DIVIDE TODAY. BREEZY CONDITIONS WILL EXACERBATE FIRE WEATHER CONCERNS PARTICULARLY ALONG THE SOUTHERN WIND CORRIDOR. HOWEVER...RED FLAG CRITERIA IS NOT EXPECTED TO BE MET EXCEPT IN ISOLATED FAVORED AREAS. WEST OF THE DIVIDE...ISOLATED SHOWERS AND A FEW AFTERNOON THUNDERSTORMS ARE POSSIBLE AS MONSOON MOISTURE RETURNS OF THE AREA. SUNDAY WILL SEE COOLER TEMPERATURES BRINGING HUMIDITY ABOVE CRITICAL LEVELS IN MOST AREAS. SHOWERS AND THUNDERSTORMS WILL BE A BIT MORE MORE WIDESPREAD IN THE WEST DURING THE AFTERNOON AND EVENING HOURS. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...BERC LONG TERM...AR AVIATION...LIPSON FIRE WEATHER...BERC
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 1046 AM MDT SAT OCT 1 2011 WYZ001>020-022>030-021300- 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- 1046 AM MDT SAT OCT 1 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT ISOLATED AFTERNOON AND EVENING THUNDERSTORMS ARE EXPECTED IN THE WEST. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY SUNDAY...ISOLATED AFTERNOON AND EVENING THUNDERSTORMS IN THE WEST AND SOUTH. MONDAY AND TUESDAY...ISOLATED AFTERNOON AND EVENING THUNDERSTORMS IN THE WEST AND SOUTH. WEDNESDAY...A CHANCE OF AFTERNOON AND EVENING THUNDERSTORMS WEST AND SOUTH. THURSDAY...A CHANCE OF SHOWERS AND A FEW THUNDERSTORMS. FRIDAY...A CHANGE TO COLDER AND WETTER WEATHER. THIS MEANS A CHANCE OF RAIN AND MOUNTAIN SNOW AND MUCH COLDER HIGH TEMPERATURES. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT. TEAM RIVERTON
The Pocatello radar (KSFX), 134 km away, was scanning. The volume nearest the first event began at 21:08 UTC.
1 thunderstorm wind. Local standard time, as filed.
A trained spotter reported a large tree snapped by a thunderstorm wind gust. The tree fell on a shed, causing significant damage to the roof and moving it slightly off its foundation.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2011Every state in 2011This day in weather historyWarnings in Wyoming, October 2011
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: 350271.