Favorable northwest flow traveled down the Wind River Valley and produced strong wind in and around Riverton. An estimated gust of 71 mph tore a roof from a home that was under construction northwest of Riverton.
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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.
Favorable northwest flow traveled down the Wind River Valley and produced strong wind in and around Riverton. An estimated gust of 71 mph tore a roof from a home that was under construction northwest of Riverton. Also, a large 50-year-old-plus spruce tree was toppled onto two vehicles parked in downtown Riverton. Both vehicles sustained damage. Other notable wind gusts of 62 mph at the NWS office and 59 mph at Riverton Regional Airport were recorded between 1430 and 1500MST.
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 Jan 11, 2:22 AM MST, 10 hours 38 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 222 AM MST SUN JAN 11 2009 .SHORT TERM...TODAY THROUGH TUESDAY NIGHT STRONG NWLY FLOW ALOFT TO CONTINUE OVER WYOMING EARLY PART OF THIS FORECAST PERIOD. PLENTY OF UPSTREAM MOISTURE TO RESULT IN OCNL SNOW OVER THE WESTERN MOUNTAINS AND VALLEYS WITH PERIODS OF MID TO HIGH LVL CLOUDS EAST OF THE DIVIDE THROUGH MONDAY. ISENTROPIC LIFT CONTINUES ALONG THE WEST AND NORTHWEST SLOPES...ALTHOUGH MID LVL SUPPORT NOT THAT IMPRESSIVE THIS AFTERNOON AND EVENING. AS A RESULT...COULD BE A BREAK IN SNOWFALL BEFORE NEXT SHORT WAVE IMPACTS THIS REGION TONIGHT. EVEN NEXT WAVE LOOKS TO RESULT ONLY IN MODEST FORCING/UPGLIDE OVER THE NORTHERN AND WESTERN MOUNTAINS OF RIW CWA. THEREFORE...NO WX HIGHLIGHTS TO MENTION AT THIS TIME...BUT A FEW INCHES OF NEW SNOW LIKELY BY MONDAY MORNING. IT IS IMPORTANT TO MENTION THAT THIS NWLY FLOW PATTERN OFTEN RESULTS IN BREEZY TO WINDY CONDITIONS ACROSS PARTS OF THE WIND RIVER BASIN...INCLUDING RIVERTON. SEE THIS CONTINUING LATER TODAY INTO THIS EVE...SO BUMPED UP WINDS IN THE GRIDS. THIS SHOULD ALSO HOLD TRUE FOR PARTS OF THE ABSAROKA MOUNTAINS WHERE STRONG WINDS HAVE BEEN A CONSTANT LATELY. MODELS THEN CONTINUE TO ADVERTISE BUILDING HEIGHTS AND AMPLIFYING RIDGE OVER THE INTERIOR WESTERN UNITED STATES MONDAY NIGHT AND TUESDAY WITH DRIER AIR PUSHING INTO WESTERN WYOMING. BY TUESDAY... FLOW ALOFT LOOKS TO PUSH SHORT WAVE ENERGY FURTHER TO THE NORTH AND EAST. RESULT TO BE LESS CLOUDS AND WIND OVER THE FORECAST AREA. WILL HAVE TO KEEP WATCH OUT FOR THE BIG HORNS DURING THIS TIME FOR SOME CLOUDS AND FLURRIES BASED ON MODEL VORTICITY AND RH FIELDS. OTHERWISE...NO PCPN EXPECTED MONDAY NIGHT INTO TUESDAY NIGHT WITH TEMPS AT OR ABOVE NORMAL. EXCEPTION TO BE SNOW COVERED WESTERN VALLEYS OF WY...SO ADJUSTED GRIDS FOR THOSE LOCATIONS ACCORDINGLY. .LONG TERM...WEDNESDAY THROUGH SUNDAY THE PATTERN REMAINS HIGHLY AMPLIFIED THROUGH THE EXTENDED WITH RIDGE ALONG WEST COAST AND TROUGH OVER THE /MIDEAST CONUS. DEFORMATION AXIS TO BE OVER EASTERN WYOMING WEDNESDAY...SHIFTING EAST THURSDAY. COLD FRONT MOVES INTO NORTHEAST WYOMING WEDNESDAY NIGHT INTO THURSDAY...THOUGH MODELS KEEPING IT FURTHER EAST EACH DAY. THIS SETS UP JOHNSON COUNTY AND THE BIGHORNS TO HAVE THE BEST CHANCE OF GETTING SNOW...OTHER AREAS WILL BE DRY. MUCH DRIER AND WARMER AIR MOVES IN THURSDAY NIGHT AS THE FLOW BECOMES TOTALLY ANTICYCLONIC. WILL SEE TEMPERATURES ABOVE NORMAL FRIDAY THROUGH SUNDAY NIGHT WITH NO PRECIP. MODELS ALTERNATING BETWEEN TAKING A SHORTWAVE SOUTH OVER WYOMING SATURDAY NIGHT. HOWEVER...THIS FEATURE SERIOUSLY LACKING MOISTURE...NOT EVEN ENOUGH TO MENTION CLOUDS. && .AVIATION... VFR CONDITIONS WILL PREVAIL OVER MOST OF THE REGION THROUGH 06Z MONDAY. IN FAR WEST WY...MVFR CONDITIONS WILL PREVAIL TODAY THROUGH THIS EVENING WITH LOW CLOUDS AND AREAS OF LIGHT SNOW. THIS WILL INCLUDE THE JACKSON AIRPORT. WINDY CONDITIONS WILL OCCUR IN THE SOUTH TODAY INTO THE EARLY EVENING WITH 20 TO 30 KNOT WIND SPEEDS. THE WIND WILL PICK UP AGAIN AROUND THE RIVERTON AIRPORT EARLY SUNDAY AFTERNOON WITH 20 TO 30 KNOTS EXPECTED INTO THE EVENING HOURS. && .FIRE WEATHER... LIGHT SNOW CAN BE EXPECTED OVER THE FAR WESTERN MOUNTAINS AND YELLOWSTONE NATL PARK THROUGH TONIGHT. GUSTY WEST TO NORTHWEST WINDS WILL RESULT IN AREAS OF BLOWING AND DRIFTING SNOW WEST OF THE DIVIDE. ELSEWHERE...IT WILL BE BREEZY WITH SEASONABLE RELATIVE HUMIDITIES. THERE WILL BE NO IMPACT TO FIRE WX DURING THIS PERIOD. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...KPL LONG TERM...TWB AVIATION...AR FIRE WEATHER...KPL
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 500 AM MST SUN JAN 11 2009 WYZ001>020-022>030-121300- 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 MST SUN JAN 11 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT WINDY CONDITIONS WILL CONTINUE TODAY OVER THE WESTERN MOUNTAINS... WIND RIVER BASIN AND SWEETWATER COUNTY. SOME LIGHT CAN BE EXPECTED IN THE FAR WEST WITH LOCALLY SNOWFALL OF AN INCH OR TWO. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT. TEAM RIVERTON
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 2009Every state in 2009This day in weather historyWarnings in Wyoming, January 2009
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: 142211.