A frontal boundary moving north ahead of a low pressure system caused high-based thunderstorms with strong outflow wind. Severe wind gusts were common across the northwest quarter of Wyoming.
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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 frontal boundary moving north ahead of a low pressure system caused high-based thunderstorms with strong outflow wind. Severe wind gusts were common across the northwest quarter of Wyoming.
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 Jun 4, 11:01 AM MST, 2 hours 10 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 1201 PM MDT MON JUN 4 2012 .SHORT TERM...MONDAY THROUGH WEDNESDAY NIGHT MAINLY QUIET WEATHER IS FOUND ACROSS THE AREA THIS MORNING WITH A RIDGE OF HIGH PRESSURE OVER THE AREA. TODAY LOOKS TO BE THE WARMEST DAY SO FAR THIS YEAR FOR MANY LOCATIONS WITH PLACES LIKE RIVERTON LIKELY SEEING TEMPERATURE AT OR OVER 90 DEGREES FOR THE FIRST TIME THIS YEAR. TEMPERATURES WILL THREATEN RECORDS IN A FEW SPOTS TODAY AS WELL. AT THE SAME TIME...A WEAK FRONT THAT LAYS JUST TO THE SOUTH WILL BEGIN TO LIFT NORTHWARD ACROSS THE STATE AND BRING THE RISK OF SOME ISOLATED TO SCATTERED AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS TO MANY PLACES THIS AFTERNOON. AS FOR THE STRENGTH OF THE STORMS...THE SPC HAS DRAWN THE SLIGHT RISK AREA VERY CLOSE TO THE NORTHERN BIG HORN BASIN. IT STILL LOOKS LIKE THE BEST DYNAMICS SHOULD REMAIN TO THE NORTH AND WEST OVER WESTERN MONTANA AND NORTHERN IDAHO. HOWEVER...MODEL SOUNDINGS DO INDICATE A DECENT AMOUNT OF CAPE. INVERTED V SOUNDINGS INDICATE THE MAIN THREAT LOOKS TO BE SOME STRONG AND GUSTY DOWNBURST WINDS. NEXT SHIFT MAY HAVE TO MONITOR FOR STRONGER STORMS SINCE SOUNDINGS...ESPECIALLY IN NORTH CENTRAL WYOMING DO INDICATE A DECENT AMOUNT OF DIRECTIONAL SHEAR WITH THE WIND PROFILE. LOOK FOR BREEZY CONDITIONS THIS AFTERNOON ALTHOUGH NOTHING USUAL FOR WYOMING. THIS COULD LEAD TO SOME ELEVATED FIRE DANGER IN SPOTS BUT RELATIVE HUMIDITY SHOULD REMAIN HIGH ENOUGH TO PRECLUDE ANY FIRE WEATHER WATCHES OR WARNINGS FOR MONDAY. BY TUESDAY A COLD FRONT WILL BE MOVING INTO WESTERN WYOMING LATER IN THE DAY AS LOW PRESSURE DEEPENS OVER MONTANA AND MOVE ACROSS THE AREA DURING THE EVENING HOURS. THE RESULTANT TIGHTENING OF THE PRESSURE GRADIENT WILL LEAD TO A WINDY DAY ACROSS MANY AREAS EAST OF THE DIVIDE AS WELL AS SWEETWATER COUNTY WITH SOME. AGREE WITH THE PREVIOUS SHIFT THAT DUE TO VERY DRY AIR OVER THE STATE EAST OF THE DIVIDE SO THE PASSAGE WILL LIKELY BE DRY FOR MOST AREAS. ONE EXCEPTION MAY BE EASTERN PORTIONS OF NATRONA AND JOHNSON COUNTIES WERE MODELS ARE INDICATING SOME MOISTURE WITH FLOW AHEAD OF THE COLD FRONT..SO WE ADDED SOME ISOLATED AFTERNOON CONVECTION ALONG THE EASTERN BORDER OF THE CWA. ANOTHER THREAT WILL BE FOR DANGEROUS FIRE WEATHER WITH WIND GUSTS OVER 40 MPH AND RELATIVE HUMIDITY FALLING TO UNDER 10 PERCENT IN SOME AREAS. FIRE WEATHER WATCHES ARE A DECENT POSSIBILITY FOR TUESDAY DEPENDING ON FUEL STATUS OF THE EFFECTED AREAS. ACROSS AREAS WEST OF THE DIVIDE...THERE WILL BE ENOUGH ENERGY AND MOISTURE PRESENT FOR SOME SHOWERS AND THUNDERSTORMS. WITH THE NEGATIVELY TILTED TROUGH SOME STORMS COULD GET STRONG...ESPECIALLY NORTH OF JACKSON. BY WEDNESDAY THE FRONT WILL BE EAST OF THE AREA AND MOST AREAS WILL HAVE A DRY DAY. MODELS ARE SHOWING SOME MOISTURE MOVING IN EAST OF THE BIGHORNS WITH SOME SOUTH TO SOUTHEASTERLY LOW LEVEL FLOW ON WEDNESDAY NIGHT SO WE ADDED SOME POPS TO THOSE AREAS FOR WEDNESDAY NIGHT. .LONG TERM...THURSDAY THROUGH MONDAY GLOBAL MODELS HAVE SPED UP A WEAK SHORTWAVE THURSDAY...SHOWING THE SYSTEM QUICKLY EXITING EARLY THURSDAY. IN WAKE OF THIS SYSTEM VERY DRY LOW/MID LEVELS ARE EXPECTED TO OVERSPREAD THE FORECAST AREA. THUS A MAINLY DRY IS EXPECTED THURSDAY. HAVE KEPT SOME LOW POPS ACROSS THE NORTH...BUT THOSE CAN PROBABLY BE REMOVED IF MODELS REMAIN CONSISTENT. THE MAIN FOCUS FOR THE LONG TERM WILL THE EVOLUTION OF AN UPPER LOW PUSHING EAST ACROSS THE ALEUTIAN ISLANDS EARLY MONDAY MORNING. GLOBAL MODELS ARE IN DECENT AGREEMENT WITH THIS UPPER LOW PUSHING INTO THE PACIFIC NORTHWEST FRIDAY. MODELS ARE IN MUCH BETTER AGREEMENT TONIGHT WITH THIS UPPER LOW/TROUGH PUSHING EAST ACROSS THE INTERMOUNTAIN WEST/ROCKIES SATURDAY AND SUNDAY. THE ECMWF IS NO LONGER KEEPING THIS UPPER LOW OVER THE PACIFIC NORTHWEST LIKE IT HAS OVER THE PAST FEW RUNS. EVEN AFTER THE WAKE OF THIS SYSTEM...WEAK TROUGHINESS WILL REMAIN OVER THE AREA. AHEAD OF THIS UPPER LOW/TROUGH...DEEP SOUTHWEST FLOW WILL USHER IN VERY WARM TEMPERATURES FRIDAY...AND AREAS EAST OF THE DIVIDE SATURDAY. BOTH DAYS COULD SEE EXTREME FIRE WEATHER BEHAVIOR ESPECIALLY WHERE FUELS ARE CONSIDERED CRITICAL. THE COLD FRONT WITH THIS SYSTEM IS CURRENTLY PROGGED TO PUSH ACROSS THE AREA LATE SATURDAY INTO SATURDAY NIGHT. MODELS ARE HINTING THAT MOISTURE COULD BE LACKING AGAIN ACROSS MUCH OF THE FORECAST AREA...LIMITING THE COVERAGE OF CONVECTION. IN WAKE OF THIS FRONT...EXPECT SEASONAL TO SLIGHTLY BELOW AVERAGE TEMPERATURES SUNDAY AND MONDAY. SUNDAY AND MONDAY APPEAR TO BE RELATIVELY DRY...BUT WILL KEEP MAINLY ISOLATED MOUNTAIN POPS SINCE THE REGION REMAINS UNDER A WEAK TROUGH. && .AVIATION.../18Z ISSUANCE/ AN UNSTABLE AIRMASS WILL BRING ISOLATED THUNDERSTORMS TO NORTHERN WYOMING AND THE CASPER AREA THROUGH 03Z. TERMINALS MOST AFFECTED WILL BE KCOD...KJAC...AND KCPR ALTHOUGH KWRL COULD SEE SOME TS AS WELL. PERIODS OF MVFR/IFR IN +TSRA ARE POSSIBLE. SOUTHERLY WIND WILL DEVELOP BY 04Z AHEAD OF A STRONG TROUGH OF LOW PRESSURE. AFTER A BRIEF LULL OVERNIGHT DURING WHICH LLWS WILL DEVELOP IN AREAS THE SURFACE WIND DIMINISHES. PARTICULARLY AROUND KCOD AND KRIW. STRONGER SOUTHERLY WIND WILL RETURN BY 16Z WITH GUSTS TO 40KT POSSIBLE PARTICULARLY IN THE SOUTH. && .FIRE WEATHER... ..VERY WARM TO HOT AND BREEZY WITH AREAS OF LOW RELATIVE HUMIDITY FOR AREAS EAST OF THE DIVIDE AND SWEETWATER COUNTY ON MONDAY... ..WARM AND WINDY WITH LOW RELATIVE HUMIDITY FOR AREAS EAST OF THE DIVIDE AND SWEETWATER COUNTY ON TUESDAY... FOR TODAY...LOOK FOR A VERY WARM TO HOT DAY TODAY WITH SOME AFTERNOON BREEZES FOR MUCH OF THE AREA EAST OF THE DIVIDE TODAY AS WELL AS FOR SWEETWATER COUNTY. ALTHOUGH RELATIVE HUMIDITY WILL REMAIN ABOVE 15 PERCENT FOR MANY AREAS TODAY...THERE COULD BE A COUPLE OF HOURS OF ELEVATED FIRE DANGER THIS AFTERNOON AND EVENING. GUSTY SHOWERS AND THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON AND EVENING. FOR TUESDAY...A POTENT COLD FRONT WILL MOVE INTO WESTERN WYOMING THIS AFTERNOON AND MOVE ACROSS THE STATE DURING THE EVENING AND NIGHTTIME HOURS. EXPECT ANOTHER VERY WARM TO HOT DAY WITH HIGH TEMPERATURES TO 90 OR ABOVE IN MANY BASIN LOCATIONS. SOUTH TO SOUTHWEST WINDS OF 25 TO 35 MPH WITH GUSTS TO OVER 40 MPH WILL BLOW ACROSS MANY AREAS. RELATIVE HUMIDITY WILL FALL TO UNDER 10 PERCENT FOR MANY AREAS EAST OF THE DIVIDE AND IN SWEETWATER COUNTY. WEDNESDAY LOOKS TO BE A COOLER DAY WITH SOMEWHAT HIGHER HUMIDITY. WINDS WILL STILL BE BREEZY BUT MUCH LIGHTER THAN ON TUESDAY. && .RIW WATCHES/WARNINGS/ADVISORIES... FLOOD WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY AFTERNOON WYZ004-006. && SHORT TERM...HATTINGS LONG TERM...WM AVIATION...BERC FIRE WEATHER...HATTINGS
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 500 AM MDT MON JUN 4 2012 WYZ001>020-022>030-051200- 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 MON JUN 4 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT SIGNIFICANT RISES ON AREA CREEKS AND RIVERS WILL CONTINUE... ESPECIALLY ACROSS THE BIG HORN BASIN. MINOR LOW LAND FLOODING IS POSSIBLE IN A FEW LOCATIONS...INCLUDING BUT NOT LIMITED TO... MEDICINE LODGE...SHELL AND TENSLEEP CREEKS...THE NORTH AND SOUTH FORK OF SHOSHONE RIVER...AND ALONG THE WIND RIVER NEAR DUBOIS. ISOLATED AFTERNOON AND EVENING THUNDERSTORMS ACROSS THE AREA. THE MAIN HAZARD WILL BE STRONG GUSTY WINDS. HOWEVER...THUNDERSTORMS ACROSS THE NORTHWEST AND THE BIGHORN BASIN COULD BE ON THE STRONG SIDE WITH STRONG WINDS AND HAIL. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY TUESDAY...WIDESPREAD ELEVATED FIRE WEATHER BEHAVIOR WHERE FUELS ARE CRITICAL. STRONG THUNDERSTORMS POSSIBLE IN THE WEST. FRIDAY AND SATURDAY...EXTREME FIRE WEATHER BEHAVIOR POSSIBLE. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ENCOURAGED TO REPORT ANY SIGNIFICANT WEATHER... INCLUDING HAIL...STRONG WINDS...ANY DAMAGE...AS WELL AS ANY FLOODING ALONG ANY CREEK OR RIVER. THANK YOU. TEAM RIVERTON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 124 PM MDT MON JUN 4 2012 WYZ015-017-018-042200- LANDER FOOTHILLS-WIND RIVER BASIN-WIND RIVER MOUNTAINS EAST- 124 PM MDT MON JUN 4 2012 SHOWERS AND THUNDERSTORMS WILL FORM AND MOVE THROUGH THE WIND RIVER BASIN THROUGH 4 PM. THE MAIN THREATS WITH THESE STORMS WILL BE GUSTY WIND TO 50 MPH...SMALL HAIL TO ONE HALF INCH IN DIAMETER...AND FREQUENT DANGEROUS CLOUD TO GROUND LIGHTNING. TAKE PROTECTIVE ACTION IF THUNDERSTORMS APPROACH. IF TRAVELING...SLOW DOWN AND TURN ON LIGHTS IN HEAVIER RAIN AS VISIBILITY CAN BE REDUCED AND WET ROADS CAN RAPIDLY BECOME SLICK. DSB
The Riverton/Lander radar (KRIW), 72 km away, was scanning. The volume nearest the first event began at 20:12 UTC.
7 thunderstorm wind. Local standard time, as filed.
An automated station on South Pass recorded a 61 mph wind gust as a result of outflow wind from a thunderstorm moving from Sweetwater County into Fremont County.
A peak wind gust to 61 mph was measured at Lander Hunt Field as a thunderstorm moved off the Wind River Range and across the town of Lander.
A thunderstorm formed over the Wind River Basin and moved north over the Owl Creek Mountains producing a 63 mph wind gust at an automated station on Boysen Peak.
A thunderstorm formed over the Wind River Basin and moved north over the Owl Creek Mountains producing a wind gust of 62 mph at an automated station on the west side of Thermopolis.
Thunderstorm outflow produced a 64 mph wind gust at Worland Municipal Airport.
A microburst associated with a strong thunderstorm that developed near Rafter J Ranch and swept north caused widespread tree and property damage. Most of the damage was concentrated in Jackson and in a swath from south of town to the northwest of town toward Teton Village. Dozens of uprooted trees caused minor roof damage and a carport collapsed at Jackson Hole Lodge in Jackson.
Several trees were downed as strong thunderstorm outflow wind reached Yellowstone National Park Headquarters at Mammoth Hot Springs.
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, June 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: 389534, 389535, 389530, 389524, 389531, 389550, 389521.