Weak, high-based thunderstorms formed in a dry environment across much of the area east of the Continental Divide. Some of these storms produced severe outflow wind gusts.
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.
Weak, high-based thunderstorms formed in a dry environment across much of the area east of the Continental Divide. Some of these storms produced severe outflow wind gusts.
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 Apr 24, 11:15 AM MST, 2 hours 6 minutes earlier.
AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE RIVERTON WY 1215 PM MDT TUE APR 24 2012 .SHORT TERM...TODAY THROUGH THURSDAY NIGHT AN UPPER LOW WILL APPROACH THE NORTHWESTERN US COAST TODAY AS A SECOND UPPER LOW DIGS SOUTH ALONG THE CALIFORNIA COAST...THESE TWO DISTURBANCES WILL WORK TO PUSH THE LARGE UPPER LEVEL RIDGE CURRENTLY OVER THE INTERMOUNTAIN WEST EASTWARD INTO THE PLAINS...BUT THE TROUGH ITSELF WILL NOT REACH THE STATE UNTIL THURSDAY...BRINGING ABOUT MUCH COOLER TEMPERATURES AND A WIDESPREAD CHANCE OF RAIN...MIXING WITH SNOW ACROSS THE WEST. OVER THE NEXT COUPLE OF DAYS...A SERIES OF WEAK DISTURBANCES WILL RIDE ALONG THE PERIPHERY OF THE RIDGE...WORKING TO BREAK IT DOWN AS WELL AS PROVIDE A FOCUS FOR MORE CONVECTIVE ACTIVITY. MODEL SOUNDINGS STILL SHOW THE CLASSIC INVERTED V SIGNATURE WITH EXPECTED CLOUD BASES AT 10-12K FEET TODAY...ESPECIALLY ACROSS CENTRAL...EASTERN AND NORTHERN WYOMING. A SLIGHT INCREASE OF LOW TO MID LEVEL MOISTURE WILL BE SEEN ACROSS THE WEST AND SOUTH TODAY...LOWERING CLOUD BASES THERE TO A MORE REASONABLE 6-8K FT AGL. MID LEVEL MOISTURE WILL ALSO INCREASE...LEADING TO MUCH MORE WIDESPREAD THUNDERSTORM ACTIVITY. AN INCREASE IN WET THUNDERSTORM ACTIVITY CAN BE EXPECTED ACROSS THE SOUTHWEST AND WEST WITH MAINLY DRY THUNDERSTORMS EXPECTED ELSEWHERE. GUSTY OUTFLOWS CAN BE EXPECTED WITH MOST STORMS...THEY COULD BE STRONG AT TIMES BUT NOTHING EXTRAORDINARY OR DAMAGING IS EXPECTED. A NORTHERLY PUSH ARRIVES ON WEDNESDAY...WHICH WILL REALLY DO SOME WORK ON INCREASING THE LOW LEVEL MOISTURE...ESPECIALLY NORTH OF THE WIND RIVER RANGE. HOWEVER...THE INCREASE IN MOISTURE WILL PROVIDE MORE FUEL TO THE CONTINUED UNSTABLE CONDITIONS...SPARKING OFF MORE THUNDERSTORMS WITH WETTING RAINS. WHICH IN CONJUNCTION WITH THE RECENT WARM TEMPERATURES COULD BRING DOWN A GOOD CHUNK OF THE REMAINING SNOWPACK. BUT AS IT STANDS NOW...THERE IS ENOUGH ROOM IN THE RIVERS TO HANDLE THE EXPECTED RUNOFF. THE BIG SHOW ARRIVES ON THURSDAY IN THE FORM OF AN UPPER LEVEL TROUGH AND ASSOCIATED COLD FRONT. THERE WILL BE PLENTY OF MOISTURE AND PLENTY OF INSTABILITY WITH THIS TROUGH...NOT MUCH OF THE STATE WILL ESCAPE A BOUT OF RAIN AND POSSIBLY MIXED PRECIPITATION ACROSS THE HIGHER ELEVATIONS OF THE WEST AS H7 TEMPS COULD DROP TO -8DEG C LATE THURSDAY NIGHT AS A COLD FRONT RUSHES WEST TO EAST ACROSS THE STATE. .LONG TERM...FRIDAY THROUGH TUESDAY FRIDAY...COOLER WITH NUMEROUS MOUNTAIN SNOW SHOWERS...SCATTERED VALLEY/BASIN RAIN AND SNOW SHOWERS NORTH AND CENTRAL. ISOLATED RAIN SHOWERS SOUTH. SATURDAY THROUGH MONDAY...CONTINUED COOL AND UNSETTLED WITH NUMEROUS SNOW SHOWERS NORTH AND CENTRAL MOUNTAINS...ISOLATED TO SCATTERED RAIN AND SNOW SHOWERS VALLEYS AND BASINS. TUESDAY...MILDER WITH CHANCES OF RAIN AND SNOW SHOWERS WEST...AND NORTHERN MOUNTAINS. MEDIUM-RANGE GLOBAL MODELS SHOW FAIRLY GOOD AGREEMENT ON 00Z RUNS BUT HAVE YET TO STABILIZE ON A CONSISTENT SOLUTION ON PACIFIC TROUGH SHEARING ACROSS THE NORTHERN ROCKIES UNDER UPPER RIDGE OVER CENTRAL CANADA. THERE IS AN OVERALL CONTINUED TREND TOWARD MUCH LESS PROGRESSION IN THE NORTHERN STREAM WITH UPPER RIDGE HOLDING AND STRENGTHENING OVER CENTRAL CANADA/NORTHERN PLAINS FRIDAY AND SATURDAY. UPPER LOW MOVING INTO THE GULF OF ALASKA EARLY THIS MORNING SPLITS AROUND THE BACKSIDE OF THIS RIDGE WITH SOUTHERN PORTION SHEARING SOUTHEAST INTO THE NORTHERN ROCKIES FRIDAY...BECOMING TRAPPED OVER WYOMING/MONTANA UNDER THE UPPER HIGH...OR A HIGH OVER LOW REX BLOCK...ON SATURDAY. UPPER LOW THEN FILLS AND EVENTUALLY LIFTS OUT INTO THE NORTHERN PLAINS ON MONDAY. FLOW ACROSS NORTH AMERICA FORECAST TO DEAMPLIFY CONSIDERABLY BY TUESDAY WITH ZONAL FLOW SETTING UP ACROSS THE EASTERN PACIFIC INTO THE NORTHERN PLAINS. FORECAST CONFIDENCE IS STILL RATHER LOW IN THIS WHOLE SCENARIO WITH MODELS SHOWING REASONABLE AGREEMENT ON THE LATEST RUNS...HOWEVER RUN-TO-RUN CONSISTENCY HAS BEEN LACKING. THE BIG PICTURE IS AN END TO UNSEASONABLY WARM TEMPERATURES AND THE SUMMER-LIKE PATTERN OF LATE...AND A RETURN TO MORE APRIL-LIKE WEATHER...UNSETTLED...SHOWERY AND COOL WEATHER FRIDAY THROUGH MONDAY. && .AVIATION.../18Z ISSUANCE/ MAINLY VFR CONDITIONS WILL PREVAIL THROUGH 12Z WEDNESDAY. ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS WILL OCCUR THROUGH 23Z WITH THE MOST WIDESPREAD ACTIVITY EXPECTED OVER NORTHWEST WYOMING. LOCAL MVFR CONDITIONS WILL OCCUR WITH SOME THUNDERSTORMS. OUTFLOW WIND GUSTS TO 40 KNOTS WILL ALSO BE POSSIBLE NEAR STORMS AND SHOWERS. && .FIRE WEATHER... ONLY ABOUT 1 IN 10 OF THE THUNDERSTORMS ON MONDAY PRODUCED A WETTING RAIN...TODAY WILL BE SIMILAR WITH SLIGHTLY MORE MOISTURE EXPECTED TO MOVE INTO THE LOWER LEVELS ACROSS THE SOUTHWEST AND WEST...WITH THE BEST CHANCES OF WETTING RAINS OVER THE HIGHER ELEVATIONS AGAIN...THE MAIN CHANGE TODAY OVER MONDAY WILL BE THE INCREASE IN THUNDERSTORM COVERAGE...YOU ARE MORE LIKELY TO SEE A THUNDERSTORM AT ANY GIVEN POINT TODAY THAN YOU WERE YESTERDAY. A MORE SIGNIFICANT PUSH OF MID AND LOW LEVEL MOISTURE ARRIVES ON WEDNESDAY...WITH CONTINUED INSTABILITY...SO MORE THUNDERSTORMS ARE EXPECTED THOUGH THEY ARE MORE LIKELY TO BE WET ACROSS THE BOARD. A PATTERN CHANGE ARRIVES ON THURSDAY AS THE UPPER LEVEL RIDGE FINALLY IS PUSHED OUT OF THE AREA...AND IS REPLACED BY A COLD AND WET TROUGH...WITH A COLD FRONTAL PASSAGE AS WELL. AS USUAL...WINDS WILL BE STRONG AHEAD OF THE TROUGH...AND WITH AND BEHIND THE FRONT AND ITS ASSOCIATED WIND SHIFT FROM THE SOUTHWEST TO THE WEST. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...ALLEN LONG TERM...AEM AVIATION...AR FIRE WEATHER...ALLEN
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 500 AM MDT TUE APR 24 2012 WYZ001>020-022>030-251100- 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 TUE APR 24 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT ISOLATED TO SCATTERED THUNDERSTORMS EXPECTED THIS AFTERNOON AND EVENING. WINDS COULD BE GUSTY AND ERRATIC NEAR SHOWERS AND THUNDERSTORMS WHICH COULD IMPACT HIGH PROFILE VEHICLES AND LIGHTWEIGHT ARTICLES LEFT OUTSIDE IN THE WIND. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH SUNDAY WEDNESDAY...ISOLATED LATE DAY THUNDERSTORMS WITH STRONG WIND GUSTS EXCEEDING 40 MPH AT TIMES. THURSDAY AND FRIDAY...INCREASING SHOWERS AND ISOLATED THUNDERSTORMS THURSDAY AFTERNOON...CONTINUING THURSDAY NIGHT. SEVERAL INCHES OF SNOW POSSIBLE ON HIGHER MOUNTAIN PASSES THURSDAY NIGHT AND FRIDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT. TEAM RIVERTON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 1225 PM MDT TUE APR 24 2012 WYZ030-241930- EAST SWEETWATER COUNTY- 1225 PM MDT TUE APR 24 2012 A CLUSTER OF THUNDERSTORMS OVER SOUTHEAST SWEETWATER COUNTY WILL BE TRACKING NORTHEAST ACROSS INTERSTATE 80 EAST OF TABLE ROCK THROUGH 130 PM. EXPECT OCCASIONAL CLOUD TO GROUND LIGHTNING AND 40 TO 50 MPH WIND GUSTS WITH THIS STORM. ANTICIPATE SUDDEN CROSS WINDS IF TRAVELING ALONG THIS PORTION OF INTERSTATE 80 AND SURROUNDING HIGHWAYS. LIPSON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 102 PM MDT TUE APR 24 2012 WYZ017-241930- WIND RIVER BASIN- 102 PM MDT TUE APR 24 2012 A DEVELOPING THUNDERSTORM OVER BEAVER RIM WILL BE MOVING NORTHEAST ACROSS THE GAS HILLS AREA THROUGH 130 PM. EXPECT OCCASIONAL CLOUD TO GROUND LIGHTNING AND 40 TO 50 MPH WIND GUSTS WITH THIS STORM. ANTICIPATE SUDDEN CROSS WINDS IF TRAVELING ALONG HIGHWAYS 135 AND 136 SOUTH AND EAST OF RIVERTON. LIPSON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 148 PM MDT TUE APR 24 2012 WYZ004>006-242030- NORTH BIG HORN BASIN-SOUTHEAST BIG HORN BASIN- SOUTHWEST BIG HORN BASIN- 148 PM MDT TUE APR 24 2012 SCATTERED THUNDERSTORMS WILL BE FOUND ACROSS THE BIG HORN BASIN THIS AFTERNOON...MOVING GENERALLY FROM THE SOUTHWEST TO THE NORTHEAST AT AROUND 20 MPH. THUNDERSTORMS WILL HAVE THE POTENTIAL TO CONTAIN DANGEROUS CLOUD TO GROUND LIGHTNING...SMALL HAIL...AND GUSTY WIND UP TO 45 MPH. THOSE WITH OUTDOOR INTERESTS ARE ENCOURAGED TO SEEK A STURDY SHELTER IF STORMS ARE ENCOUNTERED. BRANHAM
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 204 PM MDT TUE APR 24 2012 WYZ001-242130- YELLOWSTONE NATIONAL PARK- 204 PM MDT TUE APR 24 2012 THUNDERSTORMS WILL CONTINUE TO TRAIN FROM SOUTHWEST TO NORTHEAST ACROSS THE FAR NORTHWEST PORTION OF YELLOWSTONE PARK THROUGH 330 PM THIS AFTERNOON. EXPECT OCCASIONAL CLOUD TO GROUND LIGHTNING... LOCALLY HEAVY RAINFALL AND SMALL HAIL AS WELL AS 30 MPH WIND GUSTS. LIPSON
The Riverton/Lander radar (KRIW), 158 km away, was scanning. The volume nearest the first event began at 20:23 UTC.
5 thunderstorm wind. Local standard time, as filed.
A high-based thunderstorm moved along Interstate 80 producing a severe wind gust at a sensor near Bitter Creek.
A weak high-based thunderstorm moved off the Wind River Range and collapsed, producing a severe wind gust at an automated station in Crowheart.
A thunderstorm formed over the Bighorn Mountains and tracked east along the Sheridan/Johnson County line. This storm produced a severe wind gust as it crossed Interstate 90 near Piney Creek.
A weak high-based thunderstorm moved over the northern Absaroka Mountains. This storm produced a severe wind gust at the Crandall RAWS site.
A thunderstorm rolled across the northern Big Horn Basin and produced a severe wind gust at an automated station in Powell.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2012Every state in 2012This day in weather historyWarnings in Wyoming, April 2012
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: 377153, 377154, 377159, 377160, 377162.