Thunderstorms erupted in western Natrona County near the Rattlesnake Hills and moved east toward Casper. One storm strengthened rapidly and then quickly collapsed west of town.
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.
Thunderstorms erupted in western Natrona County near the Rattlesnake Hills and moved east toward Casper. One storm strengthened rapidly and then quickly collapsed west of town. Outflow wind from the collapsing storm gusted between 50 and 64 mph.
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 8, 1:51 PM MST, 10 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 251 PM MDT MON SEP 8 2014 .SHORT TERM...TONIGHT AND TUESDAY MOISTURE SURGING NWD OVER THE PAST 12 HOURS INTO NRN UT AND ALSO INTO CENTRAL NV AHEAD OF OUR TROUGH COMING ON THE WEST COAST. THIS TROUGH IS EXPECTED TO OPEN UP AND MOVE EAST ACROSS OUR AREA DURING THE DAY TUESDAY. WEAK RIPPLES AHEAD OF IT AND SEVERAL JET STREAKS WILL HELP AID IN CONVECTION. ONE MAY PROVIDE SOME SUPPORT IN OUR NRN ZONES THIS EVENING AND THEN MOVING ACROSS THE SOUTH TONIGHT INTO TUESDAY MORNING. BEST MOISTURE AND LIFT WILL BE ACROSS THE SOUTH WHERE SHOWERS AND THUNDERSTORMS ARE LIKELY TONIGHT AND ACROSS OUR FAR SERN ZONES INTO TUESDAY MORNING. HOW FAR NORTH THIS SRN BAND GETS IS ONE OF THE CHALLENGES. COULD SEE IT KNOCKING ON THE DOORSTEP OF LANDER AND RIVERTON BY MORNING BEFORE IT GETS SHUNTED OFF TO THE SE. RAINFALL IN THE FAR SOUTH...ESPECIALLY THE SOUTH HALF OF SWEETWATER COUNTY COULD EASILY TALLY A QUARTER TO HALF INCH WITH LOCAL ONE INCH AMOUNTS. THE EXPECTED CONVECTION IN THE FAR WEST WILL ALSO HAVE TO BE WATCHED AS IT MOVES INTO THE DIVIDE AREA OVERNIGHT. BEEFED UP POPS IN A LOT OF THE WEST AND SOUTH TO ACCOMMODATE THIS. THE COLD AIR TO OUR NORTH IS ALREADY INTO NRN MT AND WE EXPECT IT TO MAKE IT TO THE NRN WYO BORDER BY 12Z OR SO. THE FRONT WILL DROP SLOWLY SOUTH THROUGH MOST OF OUR NRN ZONES TUESDAY MORNING AND THEN DOWN INTO NATRONA COUNTY DURING THE AFTERNOON. FRONT MAY ALSO EDGE INTO THE NRN WIND RIVER BASIN AT SOME POINT IN THE MID TO LATE AFTERNOON. SHOWER AND THUNDERSTORMS WILL BE ON THE INCREASE ACROSS THE NRN MOUNTAINS DURING THE DAY TUESDAY WITH SHOWERS AND ISOLATED THUNDERSTORMS STARTING TO MOVE INTO THE LOWER ELEVATIONS OF THE NORTH LATE IN THE DAY. STORMS TODAY WILL STILL HAVE TO BE WATCHED FOR STRONG WIND GUSTS WITH TEMP/DP SPREADS ALREADY EXCEEDING 40 DEGREES...ESPECIALLY EAST OF THE DIVIDE. HIGHER MOISTURE LEVELS WILL LIKELY RESULT IN LESS GUSTY STORMS TUESDAY. .LONG TERM...TUESDAY NIGHT THROUGH MONDAY AN INTERESTING AND CHALLENGING BEGINNING TO THE FORECAST PERIOD WITH A SUDDEN INTRODUCTION INTO THE FIRST ROUND OF WYOMING WINTER. THE FIRST OF TWO SLUGS OF COLDER TEMPERATURES AND INCREASED MOISTURE IMPACTS THE FORECAST AREA TUESDAY NIGHT...ESPECIALLY NORTHEASTERN WYOMING. MUCH COLDER AIR IS ASSOCIATED WITH THIS SYSTEM...BRINGING SNOWFALL ACROSS THE NORTHERN MOUNTAINS. AS THE SYSTEM DEEPENS ON WEDNESDAY...EXPECT CONTINUED SHOWER ACTIVITY ACROSS THE NORTHEAST. SNOWFALL COULD BE SIGNIFICANT AT TIMES...AND MAY HAVE ADVERSE IMPACTS ON ROADWAYS. SNOWFALL ON WEDNESDAY THROUGH WEDNESDAY NIGHT COULD BE SIGNIFICANT...ESPECIALLY OVER THE BIG HORN MOUNTAINS. SOME AREAS COULD SEE 6 TO 12 INCHES WITH THIS EVENT...WITH ISOLATED AREAS EXPERIENCING MORE SIGNIFICANT SNOWFALL. NO HIGHLIGHTS ARE CURRENTLY IN EFFECT FOR ANY PORTION OF NORTHEASTERN WYOMING...THOUGH THE SCENARIO CONTINUES TO BE MONITORED. IN ADDITION...COOLING TEMPERATURES WILL BRING SOME SUB FREEZING TEMPERATURES WEDNESDAY NIGHT...ESPECIALLY ACROSS THE NORTHERN THIRD OF THE FORECAST AREA. THESE COOLER TEMPERATURES MAY PRODUCE A KILLING FROST FOR ASSOCIATED VEGETATION. AS THE FIRST SURGE OF MOISTURE LEAVES THE AREA...THE NEXT SURGE WILL BE RIGHT ON ITS HEELS...IMPACTING NORTHERN WYOMING ON THURSDAY. THE SECOND SURGE OF MOISTURE WILL MOVE INTO THE AREA THURSDAY MORNING...KEEPING MORE WIDESPREAD SHOWER ACTIVITY ACROSS THE NORTHEASTERN HALF OF THE FORECAST AREA...AND CONTINUING THE TREND OF COOLING TEMPERATURES. ADDITIONAL LOCATIONS MAY EXPERIENCE A KILLING FROST THURSDAY NIGHT...WITH SUBFREEZING TEMPERATURES EXPECTED TO IMPACT THE VAST MAJORITY OF THE FORECAST AREA. SNOWFALL WILL CONTINUE ACROSS THE NORTHEAST...WITH ANOTHER ROUND OF SIGNIFICANT PRECIPITATION POSSIBLE. STAY TUNED FOR ADDITIONAL UPDATES REGARDING THESE TWO UPCOMING SYSTEMS. ONCE THESE SYSTEMS EXIT THE AREA ON FRIDAY...A MORE BENIGN WEATHER PATTERN DEVELOPS. BUILDING NORTHWEST FLOW ASSOCIATED WITH AN AREA OF HIGH PRESSURE WILL BE IN PLACE...WITH DRY AND WARMING CONDITIONS EXPECTED INTO EARLY NEXT WEEK. && .AVIATION.../00Z ISSUANCE/ SHOWERS AND STORMS WILL CONTINUE TO DEVELOP AND INCREASE IN COVERAGE THIS AFTERNOON AND EVENING ACROSS WESTERN AND SOUTHERN WY. WIDESPREAD SHOWERS AND A FEW THUNDERSTORMS WILL CONTINUE OVERNIGHT ACROSS SWEETWATER COUNTY WITH LESS COVERAGE THE FURTHER NORTH YOU GO. LOCAL MVFR CONDITIONS MAY OCCUR IN STRONGER STORMS. WIND GUSTS TO 40 KNOTS WILL BE LIKELY IN AND NEAR STORMS THROUGH THIS EVENING. SHOWERS AND ISOLATED THUNDERSTORMS WILL BE LIKELY FROM KRKS TO KCPR TUESDAY MORNING WITH MORE ISOLATED COVERAGE FURTHER NORTHWEST. SHOWERS AND THUNDERSTORMS WILL REDEVELOP OVER THE MOUNTAINS TUESDAY AFTERNOON AS A NEW COLD FRONT SLIDES SOUTH INTO NORTH CENTRAL WYOMING. && .FIRE WEATHER... ELEVATED FIRE CONCERNS WILL CONTINUE INTO THE EVENING HOURS MAINLY EAST OF THE DIVIDE WHERE IT REMAINS WARM AND DRY WITH MIN RH'S IN THE TEENS AND WHERE ISOLATED GUSTY THUNDERSTORMS MOVE ACROSS THE AREA. MOISTURE LEVELS INCREASE CONSIDERABLY LATER TONIGHT AND TUESDAY WITH MIN RH'S GENERALLY IN THE 30S AND 40S WITH A FEW 20S IN THE FAR WEST. A COLD FRONT WILL SPREAD MUCH COLDER AIR SOUTH TUESDAY INTO WEDNESDAY ACROSS ALL BUT THE SOUTHWEST ELIMINATING MOST FIRE WEATHER CONCERNS. HOWEVER...MIN RH'S WILL BE DOWN INTO THE 20S IN THE SOUTHWEST EACH AFTERNOON WITH SOME BREEZY CONDITIONS AT TIMES. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...SKRBAC LONG TERM...BRANHAM AVIATION...SKRBAC FIRE WEATHER...SKRBAC
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 203 PM MDT MON SEP 8 2014 WYZ001>020-022>030-091200- 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- 203 PM MDT MON SEP 8 2014 THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT ISOLATED TO WIDELY SCATTERED AFTERNOON AND EVENING THUNDERSTORMS... MAINLY ACROSS THE WESTERN AND SOUTHERN HALF OF THE FORECAST AREA. HEAVY RAIN WILL BE POSSIBLE WITH SOME STORMS ACROSS THE SOUTH...GUSTY WINDS TO THE NORTH. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY 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 AND BEARTOOTH PLATEAU...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 AND IN THE CODY FOOTHILLS. 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 143 PM MDT MON SEP 8 2014 WYZ008-009-091000- BIGHORN MOUNTAINS SOUTHEAST-BIGHORN MOUNTAINS WEST- 143 PM MDT MON SEP 8 2014 ...SIGNIFICANT SNOW EXPECTED IN THE BIGHORN MOUNTAINS WEDNESDAY THROUGH THURSDAY... IT APPEARS THE INGREDIENTS ARE COMING TOGETHER FOR A SIGNIFICANT LATE SUMMER SNOWSTORM FOR THE BIGHORN MOUNTAINS BEGINNING AS EARLY AS LATE TUESDAY NIGHT AND CONTINUING THROUGH THURSDAY. A COLD...MOIST AIRMASS OVER SOUTHERN CANADA IS EXPECTED TO DROP SOUTH INTO NORTHERN WYOMING TUESDAY NIGHT AND WEDNESDAY WITH AN EVEN STRONGER SURGE OF COLDER AIR ARRIVING WEDNESDAY NIGHT AND THURSDAY. SNOW LEVELS WILL LIKELY START OUT NEAR PASS LEVEL TUESDAY NIGHT AND WEDNESDAY AND THEN FALL TO THE VALLEY FLOOR BY THURSDAY MORNING. INDICATIONS ARE THAT THE COLDEST AIR AND HEAVIEST SNOW WILL FALL WEDNESDAY NIGHT AND THURSDAY. EARLY FORECASTS POINT TOWARDS WIDESPREAD SNOWFALL OF 6 TO 12 INCHES FOR THE NORTHERN BIGHORN MOUNTAINS WITH LESSER AMOUNTS FURTHER SOUTH. FAVORED NORTHWEST FACING SLOPES COULD RECEIVE OVER A FOOT BY THE TIME THE STORM IS OVER. STAY TUNED FOR FURTHER STATEMENTS AND POSSIBLE WINTER WEATHER HIGHLIGHTS FOR THE AREA. TRAVELLERS...RANCHERS AND OTHERS WITH OUTDOOR INTERESTS SHOULD PREPARE NOW FOR THIS ABRUPT CHANGE TO WINTER LIKE CONDITIONS OVER THE NEXT COUPLE DAYS. WYZ002-091000- ABSAROKA MOUNTAINS- 143 PM MDT MON SEP 8 2014 ...HEAVY SNOW POSSIBLE OVER THE BEARTOOTH PLATEAU WEDNESDAY AND THURSDAY... A STRONG EARLY SEASON COLD FRONT WILL MOVE INTO THE AREA TUESDAY INTO TUESDAY NIGHT WITH AN EVEN STRONGER AND COLDER SYSTEM ARRIVING WEDNESDAY NIGHT. IT APPEARS THE POTENTIAL EXISTS FOR HEAVY SNOW OVER THE BEARTOOTH PLATEAU INCLUDING HIGHWAY 212 OVER BEARTOOTH PASS WEDNESDAY INTO THURSDAY. THE HIGHEST LIKELIHOOD OF HEAVY SNOW APPEARS TO BE WEDNESDAY NIGHT AND THURSDAY. EARLY INDICATIONS POINT TOWARDS 4 TO 8 INCHES OF SNOW ABOVE 9000 TO 10000 FEET WITH LOCAL AMOUNTS UP TO A FOOT. SNOW LEVELS WILL DROP TO VALLEY FLOOR BY THURSDAY MORNING SO EVEN THE FOOTHILL AREAS COULD SEE A COUPLE INCHES. TRAVELLERS...RANCHERS AND OTHERS WITH OUTDOOR INTERESTS SHOULD BE PREPARED FOR THIS ABRUPT CHANGE TO WINTER LIKE CONDITIONS OVER THE NEXT COUPLE DAYS. STAY TUNED FOR FUTURE STATEMENTS AND POSSIBLE WINTER HIGHLIGHTS. SKRBAC
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 234 PM MDT MON SEP 8 2014 WYZ020-022-082115- CASPER MOUNTAIN WY-NATRONA COUNTY LOWER ELEVATIONS WY- 234 PM MDT MON SEP 8 2014 ...SIGNIFICANT WEATHER ADVISORY FOR EASTERN NATRONA COUNTY UNTIL 315 PM MDT... AT 232 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM NEAR EMIGRANT GAP...OR 15 MILES WEST OF CASPER... MOVING EAST AT 25 MPH. WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THIS STORM. THIS STORM WILL BE NEAR... EMIGRANT GAP AROUND 245 PM MDT. U.S. HWY 20/26 MILE MARKER 10 AROUND 250 PM MDT. NATRONA COUNTY AIRPORT AROUND 255 PM MDT. RED BUTTES VILLAGE AND U.S. HWY 220 MILE MARKER 110 AROUND 300 PM MDT. PARADISE VALLEY...CENTRAL WYOMING FAIRGROUNDS AND MILLS AROUND 305 PM MDT. CASPER...JCT I25 AND HWY 20...CASPER EVENTS CENTER...HOGADON SKI AREA AND I25 EXIT 191 AROUND 310 PM MDT. EASTRIDGE MALL AROUND 315 PM MDT. THIS INCLUDES INTERSTATE 25 IN WYOMING BETWEEN MILE MARKERS 177 AND 196. IF THREATENING WEATHER APPROACHES YOUR AREA...TAKE SHELTER IN A STURDY BUILDING. REPORT HAZARDOUS WEATHER TO THE NATIONAL WEATHER SERVICE OFFICE IN RIVERTON AT 1-800-211-1448. LAT...LON 4291 10609 4267 10613 4275 10675 4293 10673 TIME...MOT...LOC 2034Z 276DEG 20KT 4283 10662 SKRBAC
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RIVERTON WY
257 PM MDT MON SEP 8 2014
WYZ020-022-082130-
CASPER MOUNTAIN WY-NATRONA COUNTY LOWER ELEVATIONS WY-
257 PM MDT MON SEP 8 2014
...SIGNIFICANT WEATHER ADVISORY FOR EASTERN NATRONA COUNTY UNTIL 330
PM MDT...
AT 255 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM NEAR CASPER...MOVING EAST AT 30 MPH.
HAIL UP TO ONE-QUARTER INCH IN DIAMETER AND WIND GUSTS UP TO 55 MPH
ARE EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN AND FREQUENT
DANGEROUS LIGHTNING. THE CASPER AIRPORT REPORTED A WIND GUST NEAR 50
MPH AT 251 PM MDT.
THIS STORM WILL BE NEAR...
EASTRIDGE MALL AROUND 300 PM MDT.
EVANSVILLE AROUND 305 PM MDT.
I25 EXIT 182 AND EDNESS K WILKINS STATE PARK AROUND 310 PM MDT.
THIS INCLUDES INTERSTATE 25 IN WYOMING BETWEEN MILE MARKERS 176 AND
201.
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 4272 10644 4298 10643 4299 10607 4298 10606
4270 10607
TIME...MOT...LOC 2057Z 269DEG 27KT 4284 10633
SKRBACThe Riverton/Lander radar (KRIW), 164 km away, was scanning. The volume nearest the first event began at 21:01 UTC.
1 thunderstorm wind. Local standard time, as filed.
Outflow from a collapsing thunderstorm produced a 10-minute stretch of wind gusts from the west-southwest that exceeded 50 mph. The ASOS at Casper-Natrona County International Airport measured a peak speed of 64 mph at 1401MST.
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: 543949.