A strong thunderstorm formed near Powell and moved northeast. Outflow wind from this storm caused damage west of Byron.
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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 strong thunderstorm formed near Powell and moved northeast. Outflow wind from this storm caused damage west of Byron.
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 2, 10:24 AM MST, 2 hours 31 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 1124 AM MDT SUN OCT 2 2011 .SHORT TERM...TODAY THROUGH TUESDAY NIGHT SHOWER ACTIVITY HAS DECREASED OVERNIGHT ACROSS WESTERN WYOMING. AREAS OF HIGH CLOUDS HAVE KEPT RADIATIONAL COOLING TO A MINIMUM AS OF THE EARLY MORNING HOURS. SUBTROPICAL MOISTURE WILL REMAIN FIRMLY IN PLACE OVER THE INTERMOUNTAIN WEST FOR THE NEXT COUPLE DAYS. WATER VAPOR IMAGERY INDICATES MOISTURE ASSOCIATED WITH THE REMNANTS OF HURRICANE HILARY HAVE BEEN ADDED TO THE MOISTURE PLUME CURRENTLY OVER ARIZONA. THE RIDGE OVER THE AREA THE LAST FEW DAYS IS BEGINNING TO BREAK DOWN AND PUSH EASTWARD. TEMPERATURES TODAY WILL REMAIN ABOVE NORMAL EAST OF THE CONTINENTAL DIVIDE BUT WILL NOT QUITE REACH RECORD TERRITORY LIKE THEY DID ON SATURDAY. THE POSSIBLE EXCEPTION WOULD BE IN NORTHERN JOHNSON COUNTY WHERE SUNDAYS RECORD HIGH OF 85 AT BUFFALO MAY BE IN JEOPARDY. WHILE H7 TEMPS WILL ONLY BE A COUPLE DEGREES COOLER TODAY...INCREASING CLOUD COVER WILL INHIBIT HEATING A BIT. EXPECT HIGHS ABOUT 5 DEGREES COOLER THAN ON SATURDAY. CONVECTION SHOULD BE A BIT MORE WIDESPREAD TODAY. INSTABILITY IS WEAKER THAN ON SATURDAY BUT A SHORTWAVE TROUGH SEEN ON W/V IMAGERY THIS MORNING OVER NORTHWEST ARIZONA WILL IMPACT WEST AND NORTHWEST WYOMING LATER TODAY BRINGING SUFFICIENT DYNAMIC FORCING FOR SCATTERED SHOWERS WITH A FEW ISOLATED THUNDERSTORMS IN THE AFTERNOON AND EVENING HOURS. A SHOWER OR TWO IS NOT OUT OF THE QUESTION EAST OF THE DIVIDE BUT ANY CONVECTION IN THESE AREAS WILL BE VERY ISOLATED AND HIGH BASED PRODUCING MAINLY VIRGA. SHOWERS AND THUNDERSTORMS CAN BE EXPECTED EACH AFTERNOON THROUGH TUESDAY WITH MOST OF THE ACTIVITY CONFINED TO AREAS WEST OF THE DIVIDE. THE NEXT MAJOR SYSTEM IS CURRENTLY LOCATED AT 41N 139W OVER THE NORTH PACIFIC. THE EFFECTS OF THIS LARGE LONGWAVE TROUGH WILL BE FELT LONG BEFORE IS COMES ASHORE AS UPPER LEVEL FLOW WILL START TO INCREASE AND BACK TO THE SOUTHWEST THEN SOUTH BY MONDAY AFTERNOON. THIS WILL BRING INCREASED WIND DURING THE AFTERNOON HOURS AS H7 FLOW OF 20 TO 30 KT MIXES DOWN TO THE SURFACE. BREEZY CONDITIONS WILL BEGIN MONDAY WITH WINDIER CONDITIONS DEVELOPING TUESDAY AFTERNOON. THE GREATEST WIND WILL BE FELT ALONG THE SOUTHERN WIND CORRIDOR FROM ROCK SPRINGS TO CASPER. .LONG TERM...WEDNESDAY THROUGH SUNDAY TROUGH DIGS INTO THE WESTERN U.S. ON WEDNESDAY WITH A SOUTH TO SOUTHWEST FLOW ALOFT OVER THE REGION. BEST CHANCE OF PRECIP WILL BE IN THE WEST AND SOUTHWEST WITH ISOLATED STORMS AS WELL. BREEZY DAY AS WELL AHEAD OF THE WEATHER SYSTEM. THE GFS AND ECMWF MODELS ARE THE CLOSEST TO EACH OTHER WITH THIS STORM THAN ANY DAYS PRIOR. THUS CONFIDENCE IS INCREASED THAT A CHANGE TO COLDER AND WETTER WEATHER IS GOING TO OCCUR. THIS CHANGE STARTS IN THE WEST AND SOUTHWEST ON THURSDAY. THEN FRIDAY WILL BE MUCH COLDER WITH A CHANCE OF RAIN AND MOUNTAIN SNOW WITH SNOW LEVELS LOWERING FRIDAY NIGHT AND SATURDAY MORNING. SATURDAY LOOKS UNSETTLED WITH SCATTERED AREAS OF RAIN AND MOUNTAIN SNOW ALONG WITH A BRISK WIND AND COOL TEMPERATURES. SUNDAY LOOKS DRY FOR MOST LOWER ELEVATIONS WITH A FEW RAIN OR SNOW SHOWERS FOR THE MOUNTAINS. EXPECT WARMER TEMPERATURES NEXT SUNDAY. && .AVIATION.../18Z ISSUANCE/ A MOVING DISTURBANCE WILL KEEP THE POTENTIAL FOR SHOWERS...THUNDERSTORMS...AND ASSOCIATED MVFR CONDITIONS ACROSS WESTERN AND SOUTHERN WYOMING THIS AFTERNOON. THESE CONDITIONS MAY BRING SHOWERS ACROSS KBPI...KPNA...KJAC...KCOD AND KRKS. THUNDERSTORMS WILL DISSIPATE BY 03Z THIS EVENING WITH THE LOSS OF DAYLIGHT. THE BIGHORN MOUNTAINS WILL SEE LINGERING SHOWERS OVERNIGHT WHICH MAY KEEP MOUNTAIN TOPS OBSCURED...AND THE BEGINNINGS OF ANOTHER SURGE OF MOISTURE WILL BRING ANOTHER ROUND OF SHOWER ACTIVITY ACROSS THE WESTERN MOUNTAINS AFTER 12Z MONDAY. && .FIRE WEATHER... MOIST CONDITIONS WILL PREVAIL OVER WESTERN WYOMING TODAY WITH SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS POSSIBLE. DRIER CONDITIONS ARE EXPECTED EAST OF THE DIVIDE BUT RH VALUES WILL INCREASE A BIT OVER SATURDAY AS TEMPERATURES WILL BE A LITTLE COOLER. WIND OF 10 TO 20 MPH WITH HIGHER GUSTS IS POSSIBLE ALONG RIDGETOPS TODAY. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL BE POSSIBLE IN THE AFTERNOON OVER THE WEST FOR THE NEXT FEW DAYS. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...BERC LONG TERM...AR AVIATION...BRANHAM FIRE WEATHER...BERC
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 500 AM MDT SUN OCT 2 2011 WYZ001>020-022>030-031200- 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 SUN OCT 2 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 AND SOUTH. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY 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...COLDER IN THE WEST WITH A CHANCE OF SHOWERS AND MOUNTAIN SNOW. A CHANCE OF SHOWERS AND A FEW THUNDERSTORMS CENTRAL AND EAST. FRIDAY AND SATURDAY...COLDER WITH A CHANCE OF RAIN AND MOUNTAIN SNOW. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT. TEAM RIVERTON
The Billings radar (KBLX), 118 km away, was scanning. The volume nearest the first event began at 19:55 UTC.
1 thunderstorm wind. Local standard time, as filed.
Two power poles were felled by a wind gust associated with outflow from a thunderstorm.
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: 350273.