A strong cold front moved south across northeast Wyoming bringing widespread high wind to northern Johnson County. Power outages were reported in the town of Buffalo.
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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 strong cold front moved south across northeast Wyoming bringing widespread high wind to northern Johnson County. Power outages were reported in the town of Buffalo. Wind gusts topped out between 60 and 66 mph in the immediate few hours following frontal passage at several reporting sites along Interstate 90. This included locations from the Sheridan County line south through Buffalo and points east.
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 19, 1:55 PM MST, 3 hours 56 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 255 PM MDT MON SEP 19 2011 .SHORT TERM...TONIGHT THROUGH THURSDAY A STRONG CANADIAN COLD FRONT IS EXPECTED TO IMPACT THE AREA THIS EVENING. AHEAD OF THIS FRONT...DRY...MILD AND WINDY CONDITIONS ARE EXPECTED ACROSS MUCH OF THE FORECAST AREA. THE COLD FRONT WILL BEGIN TO REACH INTO JOHNSON COUNTY AND THE BIG HORN BASIN DURING EARLY EVENING HOURS. THIS FRONT WILL CAUSE WIND TO SHIFT TO THE NORTH AS IT PROGRESSES THROUGH THE STATE. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ASSOCIATED WITH THIS FRONT WILL BE EXPECTED THROUGH THE OVERNIGHT HOURS AND ARE MAINLY EXPECTED TO IMPACT NORTHERN AND EASTERN WYOMING. THE FRONT WILL MOVE THROUGH THE FORECAST AREA BY THE LATE EVENING HOURS. MUCH COOLER TEMPERATURES EXPECTED ACROSS THE AREA ON TUESDAY. AS THE HIGH PRESSURE RIDGE TO THE WEST BUILDS AND SHIFTS EAST WEDNESDAY AND THURSDAY...DRY CONDITIONS WITH WARMER TEMPERATURES ARE EXPECTED. THE MODELS CONTINUE TO STRUGGLE WITH PRECIPITATION WITH THE COLD FRONT. EVEN THE HRRR AT ONE HOUR FAILS TO COME CLOSE TO MATCHING THE BAROCLINIC PRECIPITATION SHIELD OVER MONTANA. PRECIPITATION ACROSS NORTHERN AND EASTERN WYOMING MAY BECOME MORE WIDESPREAD THAN CURRENTLY FORECAST. THIS MAY ALSO IMPACT FORECAST TEMPERATURES TONIGHT AND TUESDAY. .LONG TERM...THURSDAY NIGHT THROUGH MONDAY MID AND UPPER LEVEL RIDGE STILL FORECAST OVER WYOMING AND THE ROCKIES DURING THE EXTENDED PERIOD. RIDGE AXIS WONT MOVE MUCH AND EVEN LOOKS TO HOLD ON THROUGH MONDAY OF NEXT WEEK. RESULT WILL BE DRY CONDITIONS AND ABOVE NORMAL TEMPERATURES. IN FACT...MOST OF THE LOWER ELEVATIONS SHOULD WARM INTO THE LOWER AND MIDDLE 80S WITH THIS PATTERN. THIS IS ALSO THE TIME OF YEAR WEST CENTRAL WYOMING WILL EXPERIENCE LARGE DIURNAL TEMPERATURE SWINGS. && .AVIATION... A STRONG COLD FRONT WILL MOVE FROM MONTANA INTO WYOMING TONIGHT. THIS COLD FRONT WILL BRING GUSTY WINDS AND COLDER TEMPERATURES... ESPECIALLY FOR TUESDAY AND TUESDAY EVENING. SCATTERED TO BROKEN LOW CLOUDS WILL BE ASSOCIATED WITH THIS FRONTAL PASSAGE OVER NORTHERN AND EASTERN WYOMING...POSSIBLY AS FAR SOUTH AS KCPR. OTHERWISE...VFR CONDITIONS WILL PREVAIL THE NEXT FEW DAYS. SURFACE WINDS WILL HAVE THE BIGGER IMPACT BY TUESDAY BEHIND THE FRONT. THE PRESSURE GRADIENT WILL ALLOW FOR NORTHWESTERLY WINDS GUSTING TO 30-40 MPH IN PLACES. CLEARING EAST OF THE CONTINENTAL DIVIDE BY TUESDAY AFTERNOON...THEN DRY WEATHER FOR THE REST OF THE WEEK. && .FIRE WEATHER... A STRONG CANADIAN COLD FRONT IS EXPECTED TO IMPACT THE AREA BEGINNING THIS EVENING. AHEAD OF THIS FRONT...DRY...MILD AND WINDY CONDITIONS ARE EXPECTED ACROSS MUCH OF THE FORECAST AREA. THE COLD FRONT WILL BEGIN TO REACH INTO JOHNSON COUNTY AND THE BIG HORN BASIN DURING EARLY EVENING HOURS TODAY. THIS FRONT WILL CAUSE WIND TO SHIFT TO THE NORTH AS IT PROGRESSES THROUGH THE STATE. SCATTERED SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THIS FRONT WILL BE EXPECTED THROUGH THE OVERNIGHT HOURS AND ARE MAINLY EXPECTED TO IMPACT NORTHERN WYOMING. THE FRONT WILL MOVE THROUGH THE FORECAST AREA BY THE LATE EVENING HOURS. MUCH COOLER TEMPERATURES EXPECTED ACROSS THE AREA ON TUESDAY...WITH ELEVATED DAYTIME HUMIDITY. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...C.BAKER LONG TERM...KPL AVIATION...KPL FIRE WEATHER...C.BAKER
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 649 PM MDT MON SEP 19 2011 WYZ001>020-022>030-201100- 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- 649 PM MDT MON SEP 19 2011 ...HIGH WIND WARNING IN EFFECT FOR NORTHERN JOHNSON COUNTY THROUGH 3AM TUESDAY... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT DRY...WARM AND BREEZY CONDITIONS ARE EXPECTED TODAY ACROSS MUCH OF THE AREA. THIS COMBINATION WILL ELEVATE FIRE WEATHER BEHAVIOR THIS AFTERNOON. A STRONG CANADIAN COLD FRONT WILL MOVE THROUGH THE AREA LATE THIS AFTERNOON AND EVENING...SPREADING SHOWERS AND THUNDERSTORMS ACROSS NORTHERN WYOMING...AND CAUSING A SHARP WIND SHIFT...AND WINDY CONDITIONS...ESPECIALLY ACROSS JOHNSON COUNTY. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY TUESDAY...ISOLATED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE ACROSS NORTHERN WYOMING DUE TO THE FRONTAL PASSAGE. SIGNIFICANTLY COOLER TEMPERATURES ANTICIPATED ON TUESDAY. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ENCOURAGED TO REPORT ANY SIGNIFICANT WEATHER. THANK YOU. TEAM RIVERTON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 539 PM MDT MON SEP 19 2011 WYZ002>004-008-200115- ABSAROKA MOUNTAINS-BIGHORN MOUNTAINS WEST-CODY FOOTHILLS- NORTH BIG HORN BASIN- 539 PM MDT MON SEP 19 2011 ...COLD FRONT WILL BRING STRONG GUSTY WINDS EARLY THIS EVENING... A COLD FRONT WILL PUSH SOUTH ACROSS THE MONTANA/WYOMING BORDER AROUND 6 PM...PUSHING THROUGH POWELL...COWLEY...AND LOVELL SHORTLY AFTERWARDS...AND THEN SOUTH ACROSS THE REST OF NORTHERN BIG HORN BASIN THROUGH 730 PM. EXPECT NORTH TO NORTHWEST WIND AT 25 TO 35 MPH WITH GUSTS NEAR 50 MPH TO DEVELOP BEHIND THE FRONT ALONG WITH ISOLATED TO SCATTERED SHOWERS. THE WINDS WILL GRADUALLY DIMINISH AFTER MIDNIGHT. WYZ009-010-200115- BIGHORN MOUNTAINS SOUTHEAST-NORTHEAST JOHNSON COUNTY- 539 PM MDT MON SEP 19 2011 ...COLD FRONT WILL BRING STRONG GUSTY WINDS EARLY THIS EVENING... A COLD FRONT WILL PUSH SOUTH ACROSS THE MONTANA/WYOMING BORDER AROUND 6 PM...AND ACROSS INTERSTATE 90 IN NORTHEAST JOHNSON COUNTY BETWEEN 730 PM AND 8 PM. EXPECT NORTH TO NORTHWEST WIND AT 25 TO 35 MPH WITH GUSTS NEAR 55 MPH TO DEVELOP BEHIND THE FRONT ALONG WITH ISOLATED TO SCATTERED SHOWERS. THE WINDS WILL GRADUALLY DIMINISH AFTER 3 AM TUESDAY MORNING. AEM
The national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2011Every state in 2011This day in weather historyWarnings in Wyoming, September 2011
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: 336182.