A thunderstorm developed over the Big Horn Basin, tracked east across the Bighorn Range, and onto the plains of Johnson County. This storm produced wind gusts of 58 mph at Worland Municipal Airport and 59 mph at the Poker Creek RAWS site in the foothills of the southern Bighorn Range.
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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 thunderstorm developed over the Big Horn Basin, tracked east across the Bighorn Range, and onto the plains of Johnson County. This storm produced wind gusts of 58 mph at Worland Municipal Airport and 59 mph at the Poker Creek RAWS site in the foothills of the southern Bighorn Range.
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 Sep 7, 10:00 AM MST, 2 hours 24 minutes earlier.
AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE RIVERTON WY 11 AM MDT SUN SEP 7 2014 .SHORT TERM...TODAY THROUGH TUESDAY NIGHT FLAT RIDGING WRN CONUS...MODEST TROF E W/ CLOSED/CUT OFF LOW OFF WRN COAST...UPR HIGH OVR SRN CONUS AND HURRICANE NORBERT WELL S OFF CNTRL BAJA COAST. RELATIVELY WEAK SW MOVING THRU MILD RIDGING CURRENTLY OVR CWA TONIGHT...WITH ANOTHER WEAK SW IN NRN UT AND HEADED THIS WAY...AND YET ANOTHER WEAK SW LOCATED OVR SERN OR...ALSO HEADED TOWARD WY. TODAY...SIMILAR TO SATURDAY EXCEPT A LITTLE WARMER. MOISTURE WILL STILL BE AT A PREMIUM FOR THE MOST PART...AND MOSTLY AT MID/UPR LVLS WITH SLIGHTLY BETTER VALUES ACROSS THE FAR SRN FA. INSTABILITY PROVIDED BY THE SUN AND WEAK COOLING ALOFT W/ SW ARRIVAL(S) WILL GIVE GOOD MID AFTERNOON LAPSE RATES...BUT AGAIN WILL HAVE LITTLE MOISTURE TO ACT ON. THIS WILL GIVE MAINLY ISOLATED SHRA/TSRA CHCS...MAYBE WIDELY SCATTERED IN THE CNTRL/SRN MOUNTAINS. STRONGER STORMS OF THE DAY WILL RESIDE OVER THE W CNTRL MOUNTAINS...MAINLY THE WRN WIND RIVER AND SRN ABSAROKAS. ADDITIONALLY...THE HIGH SFC TO WHATEVER LAPSE RATES AND NEAR UNIDIRECTIONAL WIND FROM THE SFC ON UP WILL ALLOW GUSTY W TO SW WINDS TO FORM ONCE AGAIN ACROSS THE SRN ZONES. ATTM...ALTHOUGH WINDS WILL BE UP AND RH WILL GENERALLY BE DOWN...FIRE DANGER CONDITIONS LOOK TO MOSTLY REMAIN BELOW CRITICAL LVLS...BUT WILL CERTAINLY BE ENHANCED. MONDAY THRU TUE NIGHT...UPR HIGH OVR SRN CONUS HELPS TO REDIRECT BOTH TROPICAL MOISTURE FROM MEXICO AS WELL AS A LITTLE MOISTURE FROM DYING HURRICANE NORBERT INTO THE DESERT SW AND EVENTUALLY INTO THE SRN HALF OF WY. AN UPSTREAM KICKER SW...NOW LOCATED OVR SERN AK...WILL ARRIVE OVR BC SUNDAY NIGHT AND BOOT OUT THE COL CURRENTLY OVR THE EPAC...WHICH WILL IN TURN OPEN THE UPR FLOW TO THE SOUTHWEST AHEAD OF THE NOW APPROACHING TROF WITH AN EMBEDDED SW/JET STREAK ALSO MOVING OVERHEAD BY MID-DAY. THIS WILL ALLOW FOR MUCH INCREASED PRECIP CHCS ACROSS THE CNTRL AND SRN FA. FROM TUESDAY THRU TUESDAY NIGHT...THIS MOISTURE WILL COMBINE WITH A MORE NORTHERLY SOURCE OF MOISTURE THAT WILL FOLLOW THE KICKER SW TO NEAR/N OF THE FA. AT THE SAME TIME...LEE CYCLOGENESIS WILL BE TAKING PLACE FROM ERN WYO DOWN INTO ERN CO. ALL THIS SHOULD GIVE A RELATIVELY BROAD AREA OF PRECIP ACROSS MUCH OF THE FA BY TUE AFTERNOON...WITH BEST CHANCES AGAIN ACROSS THE SOUTH...THEN THE CNTRL AND ERN FA IN THE EVENING AS THE MAIN TROF AXIS BEGINS TO HEAD INTO THE WRN CWA. SNOW/SNOW SHOWERS WILL BECOME INCREASINGLY LIKELY OVER THE HIGHER TERRAIN OF THE NRN MOUNTAINS TUE NIGHT AS SNOW LEVELS DROP OVERNIGHT FROM AROUND 10K FT TO 8.5 TO 9K FT...WITH 1 TO 3 INCHES LIKELY. LOW TEMPS WED MORNING WILL DROP SOME 10 TO 15 DEG OVER THOSE ON TUE MORNING...A BIT LESS ACROSS THE SRN ZONES AS A RATHER STRONG FRONT PLUNGES SWD ACROSS THE FA TUE NIGHT FOLLOWING ITS ASSOCIATED LOW INTO THE CNTRL HIGH PLAINS. .LONG TERM...WEDNESDAY THROUGH SUNDAY SYNOPSIS...A STRONG CANADIAN COLD FRONT WILL USHER IN RAIN AND SNOW SHOWERS ACROSS NORTH AND CENTRAL WYOMING ON WEDNESDAY WITH SNOW LEVELS LOWERING TO BETWEEN 7000 AND 8000 FEET ACROSS NORTHERN WYOMING. COLD CANADIAN AIR WILL CONTINUE TO SPILL EAST OF THE DIVIDE WITH SNOW LEVELS WILL LOWERING TO 5000 TO 6000 FEET ACROSS NORTHERN WYOMING WEDNESDAY NIGHT AND THURSDAY MORNING. PRECIPITATION IS EXPECTED TO TAPER OFF THURSDAY AFTERNOON/EVENING. COLD CANADIAN SURFACE HIGH PRESSURE WILL SETTLE INTO THE AREA THURSDAY NIGHT WITH A WIDESPREAD FROST/FREEZE POSSIBLE ACROSS THE CENTRAL BASINS FRIDAY MORNING. MAINLY DRY CONDITIONS WITH A WARMING TREND WILL FOLLOW FRIDAY AND SATURDAY. GFS AND ECMWF SHOW BETTER AGREEMENT WITH COLD UPPER VORTEX TAKING SHAPE OVER THE NORTHERN PLAINS WEDNESDAY AND THURSDAY. THE INITIAL SHORTWAVE/COLD POOL OVER SE ALASKA EARLY THIS MORNING WILL DROP SOUTH DOWN THE FRONT SIDE OF AMPLIFYING RIDGE OVER THE EASTERN PACIFIC TO NEAR CUTBANK BY 18Z TUESDAY...TURNING ESE ACROSS MONTANA INTO THE NORTHERN PLAINS TUESDAY NIGHT AND WEDNESDAY. A SECOND COLDER SYSTEM IS PULLED SOUTH ALBERTA INTO WESTERN MONTANA ON WEDNESDAY...BEFORE SHEARING ESE ACROSS NORTHERN WYOMING. IT IS THIS SECOND SYSTEM WHERE GFS AND ECMWF SHOW THE MOST SPREAD WITH THE GFS CONTINUING TO BE FASTER ON A FURTHER NORTHWARD TRACK...WITH THIS SYSTEM CATCHING UP TO A CLOSED H5 LOW FORMED BY THE FIRST THE FIRST SYSTEM SYSTEM OVER NORTH DAKOTA THURSDAY MORNING. ECMWF IS SLOWER WITH THIS SECOND SYSTEM...DIGGING IT FURTHER SOUTH ACROSS NORTHERN WYOMING THURSDAY MORNING BEFORE THE TWO SYSTEMS MERGE OVER THE WESTERN GREAT LAKES THURSDAY NIGHT. BOTH MODELS...THAT WERE TRENDING COLDER OVERALL OVER THE LAST COUPLE OF DAYS...HAVE TRENDED JUST A TAD WARMER THIS MORNING OR JUST SLIGHTLY HIGHER WITH 1000-500MB THICKNESSES. GEFS ENSEMBLE MEAN IS A GOOD COMPROMISE BETWEEN THE TWO DETERMINISTIC RUNS THIS MORNING WITH THE BEST CHANCES OF PRECIPITATION ACROSS THE NORTH ON WEDNESDAY...ACROSS THE NORTHERN BIG HORN BASIN TO VCNTY AND NORTH OF INTERSTATE 90 WITH SIGNIFICANT SNOW POSSIBLE ABOVE 8000 FEET IN THE BIGHORN RANGE. ANOTHER SHOT OF PRECIPITATION WIT THE SECOND COLDER SYSTEM LOOKS TO HIT THE SAME AREA AND COULD BE A MAJOR EARLY WINTER STORM FOR THE NORTHERN BIG HORN RANGE BEFORE SNOW TAPERS OFF LATER ON THURSDAY...WITH A FEW INCHES OF SNOW POSSIBLE IN THE LOWER ELEVATIONS...MAINLY NE JOHNSON COUNTY WEDNESDAY NIGHT AND THURSDAY MORNING. THERE IS LESS CONFIDENCE IN HOW MUCH PRECIPITATION WILL FALL FURTHER SOUTH ACROSS NATRONA AND FREMONT COUNTIES WEDNESDAY AND THURSDAY...AT THIS TIME IT IS LOOKING LIKE ANY PRECIPITATION WILL BE ON THE LIGHT SIDE...MOSTLY RAIN BUT COULD SEE SOME SNOWFLAKES WEDNESDAY NIGHT AND THURSDAY MORNING. AS IF THIS WASNT ENOUGH WHILE IT IS STILL OFFICIALLY SUMMER...THE CENTRAL BASINS COULD SEE THEIR FIRST WIDESPREAD FROST/FREEZE OF THE SEASON IF SKIES CLEAR OUT THURSDAY NIGHT. DETERMINISTIC RUNS ARE HINTING AT ANOTHER SHOT OF COLD CANADIAN AIR NEXT WEEKEND WHILE GEFS AND ECES MEANS ARE SHOWING A FLATTER UPPER RIDGE OVER THE WESTERN U.S. ...TROUGH OVER THE EAST. FORECAST CONTINUES THE DRY AND WARMER TREND FRIDAY INTO THE WEEKEND PER THE ENSEMBLE MEANS. && .AVIATION.../12Z ISSUANCE/ EAST OF THE DIVIDE...KCOD/KCPR/KLND/KRIW/KWRL ROUTES MAINLY VFR CONDITIONS ARE EXPECTED. AFTER 20Z...WIDELY SCATTERED SHOWERS AND STORMS WILL OCCUR THROUGH 04Z. LOCAL MVFR CONDITIONS MAY OCCUR IN STORMS. WEST OF THE DIVIDE...KBPI/KJAC/KPNA/KRKS ROUTES MAINLY VFR CONDITIONS ARE EXPECTED. AFTER 19Z...ISOLATED TO WIDELY SCATTERED SHOWERS AND STORMS WILL OCCUR THROUGH 04Z. LOCAL MVFR CONDITIONS MAY OCCUR IN STORMS. && .FIRE WEATHER... FIRE DANGER WILL BE ENHANCED ACROSS THE SOUTHEAST TO EASTERN DISPATCH ZONES TODAY AS INSTABILITY GROWS THROUGH THE DAYTIME HOURS AND SOME STRONGER WINDS ALOFT ARE BROUGHT DOWN TO THE SURFACE. AT THE MOMENT HOWEVER...BOTH WIND AND MINIMUM RH VALUES LOOK TO REMAIN JUST ABOVE CRITICAL LEVELS...WITH PERHAPS A FEW ISOLATED AREAS REACHING THESE VALUES FOR AN HOUR OR TWO. AN ISOLATED THUNDERSTORM IS ALSO POSSIBLE AGAIN ACROSS THIS REGION. ELSEWHERE...MIN RH VALUES WILL RANGE GENERALLY FROM 20 TO 30 PERCENT...EVEN WITH GUSTY WEST WINDS. MONDAY...ANOTHER DAY OF ENHANCED FIRE DANGER AS RH VALUES LOOK TO DROP A BIT FURTHER OVER THE NORTHERN AND CENTRAL BASINS IN ADDITION TO EASTERN ZONES...HOWEVER WINDS LOOK TO REMAIN BELOW CRITICAL LEVELS IN THESE AREAS. WILL MONITOR FOR CHANGES TO THIS SITUATION. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...BRAUN LONG TERM...AEM AVIATION...AR/LIPSON FIRE WEATHER...BRAUN
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 500 AM MDT SUN SEP 7 2014 WYZ001>020-022>030-081100- 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 SUN SEP 7 2014 THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT ISOLATED TO WIDELY SCATTERED MOUNTAIN THUNDERSTORMS ACROSS THE FORECAST AREA TODAY AND THIS EVENING WILL ALLOW FOR OCCASIONAL LIGHTNING STRIKES...SMALL HAIL AND GUSTY ERRATIC WINDS. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY MONDAY...ISOLATED TO WIDELY SCATTERED AFTERNOON AND EVENING THUNDERSTORMS...MAINLY ACROSS THE SOUTHERN HALF OF THE FORECAST AREA. HEAVY RAIN WILL BE POSSIBLE WITH SOME STORMS ACROSS THE SOUTH. TUESDAY...SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS SOUTH. ISOLATED SHOWERS AND STORMS CENTRAL AND NORTH. WIDELY SCATTERED TO SCATTERED SHOWERS AND ISOLATED STORMS TUESDAY NIGHT... WITH SNOW SHOWERS POSSIBLE ABOVE 8500 FEET IN THE HIGHER REACHES OF THE NORTHERN MOUNTAINS. WEDNESDAY AND THURSDAY...A STRONG CANADIAN COLD FRONT WILL BRING THE POTENTIAL FOR SIGNIFICANT SNOW IN THE NORTHERN BIGHORN RANGE...ALONG WITH HAZARDOUS WINTER DRIVING CONDITIONS OVER MOUNTAIN PASSES. A FEW INCHES OF SNOW MAY ACCUMULATE IN THE LOWER ELEVATIONS ACROSS NORTHERN WYOMING WEDNESDAY NIGHT AND THURSDAY MORNING...MAINLY ALONG AND NORTH OF INTERSTATE 90 ACROSS JOHNSON COUNTY. FRIDAY...A WIDESPREAD FREEZE OR FROST POSSIBLE ACROSS THE LOWER ELEVATIONS OF CENTRAL WYOMING FRIDAY MORNING. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT. TEAM RIVERTON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 745 AM MDT SUN SEP 7 2014 WYZ025-071445- UPPER GREEN RIVER BASIN FOOTHILLS- 745 AM MDT SUN SEP 7 2014 ...DENSE FOG AROUND BONDURANT... MORNING TRAVELLERS SHOULD BE ALERT FOR AREAS OF DENSE FOG AND SHARPLY REDUCED VISIBILITY TO ONE QUARTER MILE OR LESS FOR SHORT DISTANCES AROUND BONDURANT INCLUDING ON STATE HIGHWAY 189 AND 191. SLOW DOWN AND ARRIVE SAFELY AT YOUR DESTINATION THIS MORNING. THE FOG SHOULD LIFT AROUND 9 AM. SKRBAC
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 1144 AM MDT SUN SEP 7 2014 WYZ012-014>016-071900- TETON AND GROS VENTRE MOUNTAINS-UPPER WIND RIVER BASIN- WIND RIVER MOUNTAINS EAST-WIND RIVER MOUNTAINS WEST- 1144 AM MDT SUN SEP 7 2014 AN AREA OF SHOWERS AND SOME THUNDERSTORMS WILL BE TRACKING EAST ACROSS HIGHWAY 26 BETWEEN DUBOIS AND TOGWOTEE PASS THROUGH 1 PM THIS AFTERNOON. EXPECT LOCALLY HEAVY RAINFALL...SMALL HAIL AND OCCASIONAL CLOUD TO GROUND LIGHTNING WITH SOME OF THESE STORMS. IF OUTDOORS IN EXPOSED AREAS...SEEK SHELTER AT THE FIRST SIGN OF THREATENING WEATHER. LIPSON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 1222 PM MDT SUN SEP 7 2014 WYZ005-007-017-071900- OWL CREEK AND BRIDGER MOUNTAINS WY-SOUTHWEST BIG HORN BASIN WY-WIND RIVER BASIN WY- 1222 PM MDT SUN SEP 7 2014 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTHERN HOT SPRINGS AND NORTHERN FREMONT COUNTIES UNTIL 100 PM MDT... AT 1220 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A THUNDERSTORM 9 MILES EAST OF MAVERIK SPRING DOME FIELD...OR 19 MILES NORTH OF PAVILLION...MOVING EAST AT 30 MPH. PEA SIZE HAIL IS EXPECTED WITH THIS STORM...ALONG WITH LOCALLY HEAVY RAIN AND OCCASIONAL DANGEROUS LIGHTNING. THIS STORM WILL BE NEAR... RURAL NORTHERN FREMONT COUNTY THROUGH 100 PM MDT RURAL SOUTHERN HOT SPRINGS COUNTY THROUGH 100 PM MDT IF THREATENING WEATHER APPROACHES YOUR AREA...TAKE SHELTER IN A STURDY BUILDING. BRIEF HEAVY RAIN...WHICH MAY FLOOD LOW LYING AREAS SUCH AS DITCHES AND UNDERPASSES...IS POSSIBLE. REPORT HAZARDOUS WEATHER TO THE NATIONAL WEATHER SERVICE OFFICE IN RIVERTON AT 1-800-211-1448. LAT...LON 4361 10819 4328 10821 4343 10894 4361 10889 TIME...MOT...LOC 1822Z 281DEG 24KT 4350 10878 LIPSON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 100 PM MDT SUN SEP 7 2014 WYZ005>007-071945- OWL CREEK AND BRIDGER MOUNTAINS WY-SOUTHEAST BIG HORN BASIN WY-SOUTHWEST BIG HORN BASIN WY- 100 PM MDT SUN SEP 7 2014 ...SIGNIFICANT WEATHER ADVISORY FOR WESTERN WASHAKIE AND EASTERN HOT SPRINGS COUNTIES UNTIL 145 PM MDT... AT 1257 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM NEAR WINCHESTER...OR 14 MILES NORTH OF THERMOPOLIS...MOVING EAST AT 20 MPH. HAIL UP TO ONE-HALF INCH IN DIAMETER AND WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN AND FREQUENT DANGEROUS LIGHTNING. THIS STORM WILL BE NEAR... RURAL WESTERN WASHAKIE COUNTY THROUGH 145 PM MDT RURAL CENTRAL HOT SPRINGS COUNTY THROUGH 145 PM MDT RURAL CENTRAL WASHAKIE COUNTY THROUGH 145 PM MDT RURAL EASTERN HOT SPRINGS COUNTY THROUGH 145 PM MDT IF THREATENING WEATHER APPROACHES YOUR AREA...TAKE SHELTER IN A STURDY BUILDING. BRIEF HEAVY RAIN...WHICH MAY FLOOD LOW LYING AREAS SUCH AS DITCHES AND UNDERPASSES...IS ALSO LIKELY. DO NOT DRIVE YOUR VEHICLE ON A FLOODED ROADWAY. REPORT HAZARDOUS WEATHER TO THE NATIONAL WEATHER SERVICE OFFICE IN RIVERTON AT 1-800-211-1448. LAT...LON 4407 10768 4359 10771 4367 10826 4407 10824 TIME...MOT...LOC 1900Z 274DEG 16KT 4384 10814 SKRBAC
The Riverton/Lander radar (KRIW), 109 km away, was scanning. The volume nearest the first event began at 19:22 UTC.
2 thunderstorm wind. Local standard time, as filed.
The ASOS at the Worland Municipal Airport clocked a 58 mph wind gust from the west at 1224MST as a thunderstorm rolled east across Washakie County.
The Poker Creek RAWS site registered a wind gust to 59 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2014Every state in 2014This day in weather historyWarnings in Wyoming, September 2014
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: 539652, 534484.