Severe thunderstorms developed over higher terrain and tracked over the adjacent valleys.
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.
Severe thunderstorms developed over higher terrain and tracked over the adjacent valleys.
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 9, 2:47 PM MST, 1 hour 15 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 347 PM MDT SAT AUG 9 2008 .SHORT TERM...TONIGHT THROUGH TUESDAY CONVECTION HAS BEEN ONGOING THIS PM WITH A LOT OF PULSE STORMS SO FAR. FLOW PATTERN IS QUITE COMPLEX EAST OF THE CONTINENTAL DIVIDE. NORTHEAST FLOW AT LOW LEVELS TURNS TO N THEN NW AT MID LEVELS...THEN SOUTHWEST FLOW ABOVE 20000 FEET MSL. OVER FAR WEST WY HOWEVER...THE FLOW IS SW AT MOST LEVELS AND THE STORMS ARE MOVING FASTER. MODELS INDICATE THERE WILL BE INSTABILITY ALL THROUGH THE EVENING AND OVERNIGHT. UPPER JET ON THE NAM/GFS MODELS INDICATES A COUPLED JET STRUCTURE WITH UPPER DIVERGENCE. IF THIS VERIFIES CONVECTION A GOOD BET OVERNIGHT IN CENTRAL WY. EVENING SHIFT CAN WATCH AND SEE WHAT HAPPENS. THE FORECAST REFLECTS A GOOD CHANCE OF PRECIP IN THE WEST ZONES THROUGH THE NIGHT WITH A SLIGHT CHANCE ELSEWHERE. ON SUNDAY THE FLOW IS SW AHEAD OF THE TROUGH IN SW CANADA. THE FLOW LOOKS A BIT DIFFLUENT OVER THE CENTRAL AND EAST WITH DECENT MOISTURE PROFILE AND INSTABILITY. ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS WILL OCCUR OVER THE REGION WITH MORE ACTIVITY EAST OF THE DIVIDE. WEST OF THE DIVIDE THE ACTIVITY WILL BE ISOLATED. HAVE MADE SOME MINOR ADJUSTMENTS TO THE FORECAST TO RAISE THE PRECIP CHANCE CENTRAL AND EAST. THE ACTIVITY TO OCCUR THROUGH THE EVENING IN THE EAST WITH DECREASING STORMS IN THE CENTRAL AND WEST BY MIDNIGHT. A COOL FRONT MOVES INTO NORTHERN WY LATE SUNDAY NIGHT AND PUSHES SOUTH ON MONDAY. THE TROUGH PIVOTS INTO SOUTH CENTRAL CANADA MONDAY WITH A SHORTWAVE MOVING THROUGH MONTANA. MUCH DRIER AIR IS FORECAST OVER THE REGION MONDAY WITH ONLY THE NORTHEAST ZONES SEEING ISOLATED SHOWERS AND STORMS MONDAY AFTERNOON. MONDAY NIGHT LOOKS DRY AS DOES TUESDAY. THERE MAY BE ISOLATED CONVECTION IN JOHNSON COUNTY LATE TUE PM INTO THE EVE WITH MARGINAL INSTABILITY AND MOISTURE. AS FOR TEMPS...VERY WARM TO HOT ON SUNDAY. COOLER MONDAY AND LITTLE CHANGE IN HIGHS ON TUE. .LONG TERM...TUESDAY NIGHT THROUGH SATURDAY AN UPPER LOW IS PROJECTED BY MEDIUM RANGE MODELS TO MOVE VERY SLOWLY EAST...AND BE ACROSS SOUTHERN SASKATCHEWAN ON TUESDAY. THIS WILL RESULT IN A MAINLY DRY WESTERLY FLOW ACROSS THE AREA TUESDAY NIGHT AND WEDNESDAY. MEDIUM RANGE MODELS ARE NOW IN BETTER AGREEMENT WITH RESPECT TO THE EVOLUTION OF THIS LOW. THE ECMWF HAS TRENDED FARTHER SOUTH...MORE IN LINE WITH THE PREVIOUS/CURRENT GFS SOLUTIONS WITH THIS UPPER LOW SLOWLY PUSHING EAST SOUTHEAST INTO THE PLAINS/UPPER MIDWEST BY FRIDAY. A COUPLE OF FRONTS ARE EXPECTED WHICH SHOULD KEEP TEMPERATURES SEASONAL TO SLIGHTLY BELOW AVERAGE FROM WEDNESDAY THROUGH THE END OF THE EXTENDED. HAVE GONE SLIGHTLY ABOVE MEX MOS GUIDANCE...MORE IN LINE WITH THE SLIGHTLY WARMER ECMWF. THE 00Z ECMWF DEVELOPS A RIDGE ACROSS THE WEST...WHICH RESULTS IN A MAINLY DRY NORTHWEST FLOW BETWEEN THE RIDGE AND UPPER LOW/TROUGH THURSDAY THROUGH SATURDAY. ON THE OTHER HAND...THE GFS IS TRYING TO HINT AT A REX BLOCK WITH A WEAK LOW ACROSS THE INTERMOUNTAIN WEST AND THE HIGH ACROSS ALBERTA. THIS IN COMBINATION WITH SOME MOIST EASTERLY FLOW COULD RESULT IN PRECIPITATION RETURNING TO THE AREA. WILL HAVE ISOLATED POPS MOST AREAS THURSDAY THROUGH SATURDAY AND CAN ADJUST UP AND DOWN AS MORE CONFIDENCE IN A SOLUTION GROWS. && .AVIATION... PLUME OF MOISTURE OVER WYOMING WILL SHIFT SLIGHTLY TO THE EAST THIS AFTERNOON AND EVENING. A WEAK UPPER LEVEL DISTURBANCE WILL MOVE INTO WESTERN WY THIS AFTERNOON...AND ISOLATED SHOWERS AND THUNDERSTORMS ARE EXPECTED WEST OF THE DIVIDE THROUGH 02Z THIS EVENING. THE BEST CHANCE FOR CONVECTIVE ACTIVITY WILL BE IN THE FAR WEST...AND INCLUDED A TEMPO GROUP FOR THUNDERSTORMS IN KJAC THROUGH 02Z. WINDS WILL BECOME LIGHT TONIGHT ACROSS THE REGION...AS WEAK SURFACE HIGH PRESSURE MOVES ACROSS WYOMING. ISOLATED SHOWERS AND THUNDERSTORMS ARE EXPECTED EAST OF THE DIVIDE SUNDAY AFTERNOON AND EVENING...AS A TROUGH MOVES INTO IDAHO WITH DRIER AIR MOVING ACROSS WESTERN WYOMING. WEST WINDS WILL GUSTS TO AROUND 20 MPH SUNDAY AFTERNOON WEST OF THE DIVIDE. && .FIRE WEATHER... WIDELY SCATTERED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL OCCUR THE REST OF THE DAY INTO THE EVENING. SOME STORMS WILL HAVE WIND GUSTS TO 40 MPH AND LOCALLY HEAVY RAIN. SOME SHOWERS AND ISOLATED STORMS WILL OCCUR AFTER MIDNIGHT AS WELL. ON SUNDAY... DRIER AIR WILL WORK INTO FAR WEST WYOMING IN THE AFTERNOON. THE BETTER MOISTURE WILL REMAIN IN THE CENTRAL AND EAST. ANOTHER AFTERNOON AND EVENING OF WIDELY SCATTERED THUNDERSTORMS WILL OCCUR WITH GUSTY WIND AND LOCALLY HEAVY RAIN. A COOL FRONT WILL PASS THROUGH THE DISTRICT LATE SUNDAY NIGHT AND MONDAY. THE FRONT WILL BRING IN COOLER AIR AND A MUCH DRIER AIRMASS FOR MONDAY AND EVEN TUESDAY. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...AR LONG TERM...WM AVIATION...SMITH FIRE WEATHER...AR
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 500 AM MDT SAT AUG 9 2008 WYZ001>020-022>030-101100- 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 SAT AUG 9 2008 THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP OVER THE MOUNTAINS ONCE AGAIN THIS AFTERNOON. SCATTERED TO NUMEROUS THUNDERSTORMS WILL DEVELOP ALONG A COLD FRONT OVER NORTHWEST WYOMING THIS EVENING. THIS ORGANIZED LINE OR AREA OF STRONG STORMS IS EXPECTED TO PRODUCE HEAVY RAIN ALONG WITH SMALL HAIL. ISOLATED TO SCATTERED THUNDERSTORMS WILL CONTINUE THROUGH TONIGHT AS ATMOSPHERIC LIFT REMAINS OVER WESTERN AND CENTRAL WYOMING. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY SCATTERED SHOWERS WITH ISOLATED THUNDERSTORMS ARE EXPECTED OVER CENTRAL WYOMING SUNDAY MORNING. ISOLATED TO SCATTERED AFTERNOON AND EARLY EVENING THUNDERSTORMS ARE ANTICIPATED SUNDAY AFTERNOON... MAINLY OVER THE MOUNTAINS AND ADJACENT FOOTHILLS. DRY AIR WILL MOVE INTO THE WEST SUNDAY NIGHT AND INTO THE REMAINDER OF THE AREA MONDAY. SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ENCOURAGED TO REPORT HEAVY RAINFALL OVER A HALF AN INCH AND WIND GUSTS OVER 40 MPH FOR THE REST OF THIS EVENING. TEAM RIVERTON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 346 PM MDT SAT AUG 9 2008 WYZ028-030-092230- EAST SWEETWATER COUNTY-ROCK SPRINGS AND GREEN RIVER- 346 PM MDT SAT AUG 9 2008 ...SIGNIFICANT WEATHER ADVISORY FOR SWEETWATER COUNTY... AT 345 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM NEAR U.S. HWY 191 MILE MARKER 30...OR 13 MILES SOUTH OF FARSON...MOVING SOUTHEAST AT 15 MPH. PEA SIZE HAIL...AND WINDS AROUND 40 MPH ARE POSSIBLE WITH THIS STORM. RAINFALL AMOUNTS OF THREE-QUARTERS OF AN INCH TO ONE INCH ARE POSSIBLE WITH THIS STORM. RESIDENTS IN CENTRAL SWEETWATER COUNTY...INCLUDING THE LOCATIONS OF U.S. HWY 191 MILE MARKER 20 AND FOURTEEN MILE REST AREA...SHOULD MONITOR THE WEATHER SITUATION CLOSELY. LISTEN FOR POSSIBLE WARNINGS AND BE PREPARED TO TAKE APPROPRIATE ACTION SHOULD SEVERE WEATHER THREATEN. REPORT SEVERE WEATHER TO THE NATIONAL WEATHER SERVICE OFFICE IN RIVERTON AT 1-800-211-1448. LAT...LON 4179 10911 4172 10935 4193 10941 4195 10936 TIME...MOT...LOC 2146Z 329DEG 13KT 4193 10937 SMITH
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RIVERTON WY
400 PM MDT SAT AUG 9 2008
WYZ012-013-092245-
JACKSON HOLE-TETON AND GROS VENTRE MOUNTAINS-
400 PM MDT SAT AUG 9 2008
...SIGNIFICANT WEATHER ADVISORY FOR TETON COUNTY...
AT 357 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 8 MILES NORTHEAST OF PALISADES...OR 18 MILES WEST
OF JACKSON...MOVING NORTHEAST AT 17 MPH.
PEA SIZE HAIL IS POSSIBLE WITH THIS STORM ALONG WITH BRIEF FHEAVY
RAIN.
RESIDENTS IN SOUTHWESTERN TETON COUNTY...INCLUDING THE LOCATIONS OF
TETON PASS...TETON VILLAGE AND RENDEZVOUS PEAK...SHOULD MONITOR THE
WEATHER SITUATION CLOSELY. LISTEN FOR POSSIBLE WARNINGS AND BE
PREPARED TO TAKE APPROPRIATE ACTION SHOULD SEVERE WEATHER THREATEN.
REPORT SEVERE WEATHER TO THE NATIONAL WEATHER SERVICE OFFICE IN
RIVERTON AT 1-800-211-1448.
LAT...LON 4344 11105 4360 11106 4372 11081 4350 11067
4337 11105 4343 11106
TIME...MOT...LOC 2200Z 245DEG 15KT 4345 11110
ARSPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 448 PM MDT SAT AUG 9 2008 WYZ001-012-013-100000- JACKSON HOLE-TETON AND GROS VENTRE MOUNTAINS- YELLOWSTONE NATIONAL PARK- 448 PM MDT SAT AUG 9 2008 SHOWERS AND THUNDERSTORMS WILL DEVELOP OVER THE MOUNTAINS AND YELLOWSTONE NATIONAL PARK THROUGH 6 PM. SOME STORMS WILL MOVE ACROSS THE JACKSON VALLEY AS WELL. MODERATE TO HEAVY RAIN IS POSSIBLE WITH SOME STORMS. PEA SIZE HAIL CAN ALSO BE EXPECTED FROM THE STRONGER STORMS. SEEK SAFE SHELTER INDOORS WHEN STORMS MOVE INTO YOUR LOCATION.
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 455 PM MDT SAT AUG 9 2008 WYZ030-100000- EAST SWEETWATER COUNTY- 455 PM MDT SAT AUG 9 2008 SHOWERS AND THUNDERSTORMS WILL OCCUR OVER EASTERN SWEETWATER COUNTY THROUGH 600 PM. THE STORMS WERE DRIFTING SLOWLY SOUTH TOWARD INTERSTATE 80. THESE STORMS SHOULD IMPACT INTERSTATE 80 FROM JUST EAST OF ROCK SPRINGS TO WAMSUTTER TO THE CARBON COUNTY LINE. MODERATE TO HEAVY RAIN IS POSSIBLE WITH SOME STORMS. PEA SIZE HAIL CAN ALSO BE EXPECTED FROM THE STRONGER STORMS. SEEK SAFE SHELTER INDOORS WHEN STORMS MOVE INTO YOUR LOCATION.
The Pocatello radar (KSFX), 199 km away, was scanning. The volume nearest the first event began at 23:04 UTC.
2 hail. Local standard time, as filed.
National Park Service personnel estimated penny sized hail at the South Entrance to Yellowstone National Park.
Penny sized hail was observed near Star Valley Ranch.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2008Every state in 2008This day in weather historyWarnings in Wyoming, August 2008
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: 119004, 119005.