A severe thunderstorm formed just east of the Absaroka foothills and rumbled through northern Hot Springs County.
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 severe thunderstorm formed just east of the Absaroka foothills and rumbled through northern Hot Springs County.
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 Aug 3, 1:52 AM MST, 11 hours 3 minutes earlier.
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
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 1128 AM MDT MON AUG 3 2009 WYZ001>020-022>030-041200- 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- 1128 AM MDT MON AUG 3 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED ACROSS NORTHERN WYOMING THIS AFTERNOON AND EVENING...WHILE ISOLATED SHOWERS AND THUNDERSTORMS WILL DEVELOP ACROSS THE REMAINDER OF THE REGION. THUNDERSTORMS WILL HAVE THE POTENTIAL TO PRODUCE WIND GUSTS ABOVE 50 MPH...AND SOME HAIL THIS AFTERNOON AND EVENING. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY ISOLATED AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS ARE IN THE FORECAST FOR THIS PERIOD. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ASKED TO REPORT HAIL AND WIND GUSTS IN EXCESS OF 40 MPH FROM THUNDERSTORMS TODAY. THANK YOU. TEAM RIVERTON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 1246 PM MDT MON AUG 3 2009 WYZ002-003-031930- ABSAROKA MOUNTAINS-CODY FOOTHILLS- 1246 PM MDT MON AUG 3 2009 ...SIGNIFICANT WEATHER ADVISORY FOR PARK COUNTY UNTIL 130 PM MDT... AT 1242 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM 9 MILES SOUTHWEST OF SUNLIGHT BASIN...OR 29 MILES WEST OF CODY...MOVING EAST AT 20 MPH. ONE HALF INCH DIAMETER HAIL...AND WINDS AROUND 40 MPH ARE POSSIBLE WITH THIS STORM. THIS STORM WILL BE... 6 MILES SOUTHWEST OF STATE HWY 120 MILE MARKER 110 BY 130 PM MDT. OTHER STRONG THUNDERSTORMS OF SIMILAR MAGNITUDE WILL BE TRACKING EAST ACROSS SOUTHERN ABSAROKA MOUNTAINS AND COULD AFFECT THE DOUBLE CABIN CAMPGROUND BY 115 PM. PRECAUTIONARY/PREPAREDNESS ACTIONS... MOVE INDOORS IMMEDIATELY AS THESE STORMS APPROACHES YOUR LOCATION. IF YOU ARE IN ITS PATH...YOU SHOULD BE PREPARED FOR GUSTY WINDS...HAIL...AND DEADLY CLOUD TO GROUND LIGHTNING. IF A STURDY STRUCTURE IS NOT AVAILABLE...SEEK SHELTER IN A VEHICLE WITH THE WINDOWS UP. && REPORT HAZARDOUS WEATHER TO THE NATIONAL WEATHER SERVICE OFFICE IN RIVERTON AT 1-800-211-1448. LAT...LON 4471 10909 4446 10913 4454 10976 4472 10973 TIME...MOT...LOC 1843Z 276DEG 19KT 4462 10961 LIPSON
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RIVERTON WY
124 PM MDT MON AUG 3 2009
WYZ005-007-017-032000-
OWL CREEK AND BRIDGER MOUNTAINS-SOUTHWEST BIG HORN BASIN-WIND RIVER
BASIN-
124 PM MDT MON AUG 3 2009
AT 119 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 9 MILES SOUTHEAST OF HWY JCT 170 AND 174...OR 13
MILES WEST OF THERMOPOLIS...MOVING EAST AT 35 MPH.
WINDS OF 40 TO 50 MPH AND DEADLY CLOUD TO GROUND LIGHTNING ARE
POSSIBLE WITH THIS STORM.
AREAS AFFECTED INCLUDE...THERMOPOLIS AND HWY 789 BETWEEN THERMOPOLIS
AND BOYSEN RESERVOIR.
REPORT HAZARDOUS WEATHER TO THE NATIONAL WEATHER SERVICE OFFICE IN
RIVERTON AT 1-800-211-1448.
LAT...LON 4331 10760 4352 10860 4370 10854 4368 10772
4365 10771 4364 10760 4348 10760 4347 10757
4345 10755
TIME...MOT...LOC 1921Z 284DEG 46KT 4358 10842
BERCSPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 145 PM MDT MON AUG 3 2009 WYZ002-012-032100- ABSAROKA MOUNTAINS-TETON AND GROS VENTRE MOUNTAINS- 145 PM MDT MON AUG 3 2009 A LINE OF RAPIDLY DEVELOPING SHOWERS AND THUNDERSTORMS OVER THE GROS VENTRE AND SOUTHERN ABSAROKA MOUNTAINS WILL CONTINUE THROUGH 300 PM. FREQUENT DEADLY CLOUD TO GROUND LIGHTNING...SMALL HAIL...AND WIND GUSTS TO 45 MPH ARE ALL POSSIBLE WITH THIS LINE OF STORMS. AREAS AFFECTED INCLUDE...TOGWOTEE PASS AND DOUBLE CABIN CAMPGROUND. DSB
The Riverton/Lander radar (KRIW), 105 km away, was scanning. The volume nearest the first event began at 19:53 UTC.
1 thunderstorm wind. Local standard time, as filed.
Estimated wind gusts of 60 mph broke several three inch diameter limbs from Cottonwood trees at a ranch along Gooseberry Creek. Also, dime sized hail accumulated to a depth of two to three inches at the ranch.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2009Every state in 2009This day in weather historyWarnings in Wyoming, August 2009
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: 178008.