Copious moisture was brought north into Wyoming in strong monsoonal flow. Low-level upslope flow from the north aided the development of showers and thunderstorms.
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.
Copious moisture was brought north into Wyoming in strong monsoonal flow. Low-level upslope flow from the north aided the development of showers and thunderstorms. Atmospheric moisture values were around 200 percent of normal.
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 Jul 25, 12:58 PM MST, 1 hour 32 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 158 PM MDT WED JUL 25 2007 .SHORT TERM...TONIGHT THROUGH SATURDAY A FRESH ROUND OF CONVECTION IS TAKING PLACE IN NORTHERN WY WHICH APPEARS TO BE RAPIDLY TAKING THE PLACE OF THE REMNANTS OF LAST LAST NIGHTS CONVECTION FROM THE PREVIOUS SHORTWAVE NOW EXITING THE AREA AS NEW STRONG CONVECTION APPEAR TO BE RAPIDLY TAKING THE PLACE OF THE PATCHY MID LEVEL CLOUD TYPE. IT IS NOT TAKING MUCH HEATING FROM ANY CLEARING TO GET THINGS GOING THERE. ONE CELL OVER THE SOUTHERN BIG HORN MTNS IS ALREADY PRODUCING ENOUGH RAINFALL FOR THE RADAR TO INDICATE 1.6 INCHES OF RAINFALL FROM THESE PARTICULAR CELLS. GIVEN THE 1800 CAPES AND -3 LIFTED INDUCES PROGGED FOR OUR NORTHEAST ZONES LATE TODAY...THESE HEAVY RAIN PRODUCERS WILL LIKELY LAST THROUGH MUCH OF TONIGHT AS THE NEXT SHORTWAVE NOW MOVING INTO SOUTHWEST WY KEEP THE CONVECTION GOING. ANOTHER AREA OF THUNDERSTORMS IS STREAMING IN FROM THE SOUTHWEST INTO SOUTHWEST WY FROM THIS NEXT SHORT WAVE. THIS FEATURE WILL TRACK NORTHEAST ACROSS THE CWA THROUGH TONIGHT AND THURSDAY MORNING. THIS FEATURE WILL CONTINUE TO DRAW IN JUICY MONSOON MOISTURE WITH PW AT VALUES OF 1.6 INCHES PROGGED FOR THE NE ZONES AND OVER ONE INCH ELSEWHERE. THE NAM PF IS INDICATING 2.5 INCHES OF PRECIS FOR SOME OF THE BIG HORN MTNS THROUGH TONIGHT ALTHOUGH IF WE GET ANY AMOUNTS LIKE THAT OF COURSE THEY WILL BE MUCH MORE LOCALIZED THAN WHAT IS INDICATED BY THE MODEL. HAVE INDICATED HIGH CHIC POPS MOST AREAS WITH LIKELY POPS IN THE NORTHERN MTNS FOR TONIGHT. WITH THE TROPICAL NATURE OF THESE THUNDERSTORMS EXPECTED TO TRACK SLOWLY NORTHEAST ACROSS OUR CWA TONIGHT...THE MAIN THING TO BE ALERT FOR WILL BE HEAVY RAIN AND POSSIBLE FLASH FLOODING AS THESE STORMS TRACK THROUGH CAPES OVER 1000J/J AND LIFTED INDUCES OF AROUND -3 ALONG WITH DEW POINTS IN THE 50S WITH THE STRONGEST FOCUS OVER THE BIG HORN MTNS...NAT RONA AND JOHNSON COUNTIES ALTHOUGH ALL STORMS WILL NEED TO BE MONITORED. ON THURSDAY MORNING SCATTERED SHOWERS AND THUNDERSTORMS WILL LINGER IN SOUTHERN JOHNSON AND NAT RONA COUNTIES. A REINFORCING COLD FRONT WILL TRACK SOUTH ACROSS THE STATE TONIGHT AND WILL ACT AS A FOCUS FOR STORM DEVELOPMENT. MORE STABLE AIR WILL SHIFT SOUTH ACROSS THE STATE THURSDAY BEHIND THE FRONT WITH THE BEST CHIC OF ANY STORMS THU AFTERNOON OVER THE SOUTH AND WEST. IDLY SCOT LATE DAY STORMS EXPECTED FRIDAY AND SAT AFTERNOON. TEMPERATURES ARE ALREADY ABOUT 30 DEGREES COOLER ACROSS JOHNSON COUNTY THAN THEY WERE THIS TIME YESTERDAY. TEMPS WILL REMAIN RELATIVELY COOL BENEATH THE CLOUD COVER BEHIND THE COLD FRONT THU. TEMPS WILL BEGIN TO WARM FRIDAY AND SAT. .LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY A STAGNANT WEATHER PATTERN IS EXPECTED THROUGH THE EXTENDED FORECAST. HIGH PRESSURE ALOFT SHOULD REMAIN FROM MEXICO NORTH ACROSS THE SOUTHERN AND CENTRAL ROCKIES INTO THE NORTHERN PLAINS. A LOW PRESSURE CENTER IS EXPECTED TO REMAIN OFF THE WEST COAST OF BRITISH COLUMBIA WITH SOUTHWEST FLOW FROM NORTHERN CALIFORNIA INTO WESTERN MONTANA. THIS WILL PUT WESTERN AND CENTRAL WYOMING ON THE EDGE OF THE SUBTROPICAL MOISTURE PLUME. THIS KEEPS A THREAT OF SCATTERED TO ISOLATED AFTERNOON AND EVENING THUNDERSTORMS...MOST NUMEROUS OVER THE MOUNTAINS THROUGH THE PERIOD. LITTLE CHANGE IN TEMPERATURES ARE EXPECTED THROUGH THE EXTENDED FORECAST. THE MAIN DIFFERENCES IN THE EXTENDED MODELS ARE FOUND TO THE WEST WITH TIMING DIFFERENCES IN SHORT WAVE TROUGHS EJECTING NORTHEAST IN THE STRONGER SOUTHWEST FLOW TO THE WEST OF WYOMING. MAIN DAY TO DAY FORECAST DIFFERENCES WILL LIKELY COME FROM THE STRENGTH AND LOCATION OF CONVECTION SOUTH OF WYOMING IN THE DEEPER SUBTROPICAL MOISTURE. && .AVIATION... OUTSIDE OF WIDELY SCATTERED THUNDERSTORMS THIS EVENING...THE PATTERN WILL TURN DRIER OVER THE REGION WITH VFR CONDITIONS PREVAILING. RESTRICTED VISIBILITIES CAN BE EXPECTED NEAR ANY STORMS...BUT SHOULD REMAIN ABOVE 3NM THIS EVENING. HIGH PRESSURE WILL BE THE OVERALL MAIN WEATHER FEATURE OVER CENTRAL AND WESTERN WYOMING FROM THURSDAY INTO THE WEEKEND. && .FIRE WEATHER... SCATTERED TO NUMEROUS THUNDERSTORMS WILL OCCUR THROUGH THURSDAY MORNING PRODUCING LOCALLY VERY HEAVY RAINFALL. THESE STORMS WILL BE LAST TO END IN NAT RONA AND JOHNSON COUNTIES THURSDAY MORNING. THE HEAVIEST RAINFALL WILL LIKELY TAKE PLACE IN JOHNSON AND NAT RONA COUNTIES AS WELL AS IN THE BIG HORN MOUNTAINS. THE AIRMASS WILL BE RATHER COOL AND STABLE OVER MOST FIRE WEATHER ZONES THURSDAY BEHIND THE COLD FRONT THAT TRACKS SOUTH ACROSS THE STATE TONIGHT. ONE EXCEPTION WILL BE THE SOUTHERN AND FAR WEST ZONES THURSDAY WHERE THE AIRMASS WILL STILL BE RELATIVELY UNSTABLE WHERE WIDELY SCATTERED THUNDERSTORMS WILL TAKE PLACE. MINIMUM RELATIVE HUMIDITY WILL NOT BE BELOW THE 30S THURSDAY ANYWHERE. THE MINIMUM RELATIVE HUMIDITY WILL DROP TO THE UPPER TEENS IN THE BIG HORN BASIN FRIDAY WITH LOWER ELEVATIONS EAST OF THE DIVIDE DROPPING TO THE MID TEENS SATURDAY EAST OF THE DIVIDE. TEMPERATURES WILL WARM FRIDAY AND SATURDAY AFTER BEING 20 DEGREES COOLER THURSDAY THAN THEY HAVE BEEN FOR THE LAST COUPLE OF DAYS IN MANY AREAS. EXPECT ISOLATED TO WIDELY SCATTERED LATE DAY THUNDERSTORMS FRIDAY AND SATURDAY BUT THESE STORMS WILL NOT PRODUCE AS MUCH RAIN ALL AS THE STORMS WILL TONIGHT. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...LIPSON LONG TERM...KPL AVIATION...KPL FIRE WEATHER...LIPSON
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 501 AM MDT WED JUL 25 2007 WYZ001>020-022>030-261101- 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- 501 AM MDT WED JUL 25 2007 THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL DEVELOP AGAIN TODAY OVER MUCH OF THE AREA. A VERY MOIST AIRMASS WILL INCREASE THE POTENTIAL FOR VERY HEAVY RAIN PRODUCING THUNDERSTORMS WITH SOME LOCALIZED FLOODING POSSIBLE. OTHERWISE...FREQUENT LIGHTNING AND WIND GUSTS TO 35 MPH CAN BE EXPECTED. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY THE MONSOON WILL BEGIN TO TAPER THURSDAY WITH ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS EXPECTED. ACTIVITY FRIDAY AND INTO THE WEEKEND WILL BE MUCH MORE ISOLATED. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ASKED TO REPORT ANY FLOODING TODAY AND TONIGHT. THANK YOU. TRIW
The Riverton/Lander radar (KRIW), 152 km away, was scanning. The volume nearest the first event began at 21:30 UTC.
5 flash flood. Local standard time, as filed.
Heavy rainfall caused three separate mudslides near Valley. The mud enveloped the Valley School and trapped 15 vehicles on the South Fork Road. The slides were not entirely cleared for two days.
Heavy rainfall of over one inch fell in about 30 minutes on the west side of Dubois. Hardest hit were locations between the golf course and U.S. Highway 26. Culverts were unable to handle the heavy rain, so water flowed over the top of at least one road. Overflowing washes created temporary waterfalls pushing water and mud across Ramshorn Street (U.S. Highway 26 in Dubois). A gas station along Warm Springs Drive reported two inches of mud and water inside the associated convenience store. An antique pool table store had over one-half foot of water inside. The Dubois cooperative observer recorded 1.39 inches of rainfall during the storm. This set an all-time daily precipitation record for the station, which has recorded weather observations for nearly 90 years.
Heavy rain caused a mudslide across East Entrance Road near Sylvan Pass. The slide varied in depth from one to five feet, was about 50 feet long, and covered both lanes of the road. The road remained closed for about 14 hours until crews could open a single lane.
Rainfall estimated by radar to be three inches or more fell in a swath from Emigrant Gap to Bar Nunn. The heavy rain caused flash flooding along Poison Spider Road and other nearby roads as culverts could not handle the large volume of water. Portions of a ranch along Poison Spider Road were under several feet of water. A mobile home park south of Bar Nunn was flooded as water flowed from surrounding higher terrain. The lower floor of the rural Poison Spider Elementary School sustained flood damage as the water poured in through several doorways.
A thunderstorm produced 1.70 inches of rain in less than 30 minutes in Red Canyon. The learning center at Red Canyon Ranch was inundated with six inches of mud and water causing extensive damage. The mud, rock, and water also flooded a barn, shop, and several corrals at the ranch. Red Canyon Creek and other small tributaries were out of their banks. Road damage on the ranch was widespread. The county portion of Red Canyon Road was covered with a three-foot-deep mud flow which closed the road for much of the next week. At least one nearby residence sustained damage to a basement and destruction of their backyard landscaping due to a mud and water flow.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2007Every state in 2007This day in weather historyWarnings in Wyoming, July 2007
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: 45502, 38024, 38052, 38021, 45494.