S. Highway 287 corridor from near Muddy Gap to Beaver Rim.
Every event with a place to put it; 3 filed by county or forecast zone are drawn at its center, in a lighter ring. 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.
The combination of increasing wind aloft and a tightening surface pressure gradient generated strong wind around and west of Clark, and along the U.S. Highway 287 corridor from near Muddy Gap to Beaver Rim. Peak wind gusts of 77 to 88 mph were recorded in and near the mouth of the Clark's Fork River Canyon. Nearby, estimated peak wind gusts of 60 mph occurred just west of Clark. Sustained southwest wind of 40 to 45 mph was recorded around 0700MST by an automated sensor on Beaver Rim. Strong wind gusts increased again during the late evening at Jeffrey City, where a peak gust to 59 mph was measured at 2105MST.
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 Dec 15, 3:02 AM MST, 4 hours 8 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 302 AM MST TUE DEC 15 2009 .SHORT TERM...TODAY THROUGH THURSDAY NIGHT FAIRLY BENIGN MORNING SO FAR WITH SLIGHTLY GUSTY WIND DEVELOPING OVER CASPER...AND CHILLY TEMPERATURES NOTED OVER THE UPPER GREEN RIVER BASIN AND PINEDALE FOOTHILLS. WARMING TEMPERATURES EXPECTED TODAY FOR THE MAJORITY OF THE CWA WITH WARMER H7 TEMPERATURES MOVING OVER THE AREA. HOWEVER...LIGHT SNOWFALL WILL CONTINUE ACROSS THE WESTERN MOUNTAINS AND MAY REACH INTO THE VALLEYS. STRONG WIND WILL BE PRESENT OVER THE GREEN MOUNTAINS AND RATTLESNAKE RANGE TODAY WHERE WIND OF 35 TO 45 MPH WITH GUSTS UP TO 60 MPH POSSIBLE THROUGH THE EVENING HOURS. ADDITIONALLY...STRONG WIND WILL DEVELOP ALONG WITH THE ABSAROKA MOUNTAINS AND CODY FOOTHILLS THIS MORNING AND CONTINUE THROUGH THE AFTERNOON. MODELS CONTINUE TO INDICATE THE PRESENCE OF A MOUNTAIN WAVE WITH AN INCREASED THERMAL GRADIENT AND FAVORABLE CROSS SECTIONS AROUND THE CLARK AREA. STRONGER WIND WILL AGAIN PULSE STRONGER DURING THE LATE EVENING HOURS TONIGHT WITH POTENTIALLY DANGEROUS WIND POSSIBLE THROUGH THE EARLY MORNING HOURS OF WEDNESDAY. HIGH WIND WARNINGS ARE IN EFFECT FOR THESE AREAS TO ACCOUNT FOR THESE DANGEROUS WINDS. BREEZY WIND WILL BE POSSIBLE OVER THE LOWER ELEVATIONS OF NATRONA COUNTY. WIND OVER THIS AREA ARE EXPECTED TO REMAIN BELOW HIGH WIND CRITERIA. WIND OF 25 TO 35 MPH WITH GUSTS TO AROUND 50 MPH WILL BE POSSIBLE ACROSS THE AREA THROUGH THE AFTERNOON. WITH THE DECISION OF WIND BEING GENERALLY LESS THAN HIGH WIND CRITERIA...CANCELED THEIR HIGH WIND HIGHLIGHTS. THERE IS CERTAINLY THE OPPORTUNITY FOR ISOLATED LOCATIONS TO SEE GUSTS TO 60 MPH THIS AFTERNOON...BUT THESE WINDS SHOULD NOT BECOME WIDESPREAD. TEMPERATURES WILL CONTINUE TO WARM THROUGH THE FORECAST PERIOD...AND LIGHT SNOWFALL WILL CONTINUE ACROSS THE WESTERN MOUNTAINS AND VALLEYS. SNOWFALL ACCUMULATIONS OVER THE WESTERN MOUNTAINS MAY REACH 3 TO 5 INCHES BY WEDNESDAY AFTERNOON...WITH SOME AREAS SEEING UP TO 8 INCHES. SNOWFALL WILL CONTINUE TO MONITORED FOR THE POTENTIAL NEED FOR SNOW ADVISORIES...BUT CURRENT MODEL RUNS ARE NOT OVERLY FAVORABLE FOR THE WIDESPREAD DEVELOPMENT OF HEAVIER SNOWFALL. THE GFS MODEL DEMONSTRATES A PUSH OF MOISTURE MOVING THROUGH SOUTHERN AND EASTERN WYOMING BY THURSDAY AFTERNOON. HAVE INTRODUCED A FEW MORE AREAS OF LIGHT SHOWER ACTIVITY TO ACCOUNT FOR THIS POSSIBILITY. SNOWFALL OVER NATRONA AND JOHNSON COUNTIES LOOKS MORE FAVORABLE FOR THURSDAY EVENING...WITH INCREASED COVERAGE NOTED IN CURRENT FORECAST PACKAGE. .LONG TERM...FRIDAY THROUGH TUESDAY SOME LINGERING LIGHT SNOW FRIDAY MORNING WITH THE DEPARTING WEATHER SYSTEM THEN MOSTLY DRY FRI AFTERNOON. UPPER RIDGE TO THE WEST OF WY SATURDAY WITH NW FLOW OVER THE AREA AND POSSIBLE LIGHT PRECIP OVER THE NW MTS. THE RIDGE MOVES EAST OVER THE ROCKIES ON SUNDAY PER THE GFS MODEL. THE CANADIAN AND ECMWF KEEP NW FLOW OVER THE AREA. WILL SIDE WITH THE NW FLOW SCENARIO AS ECMWF HAS BEEN BETTER MODEL LATELY. MOISTURE IN THE NW FLOW LOOKS MARGINAL AND WILL KEEP THE LOW PRECIP CHANCE IN THE NW MTS SUNDAY AS WELL. WEATHER PATTERN GETS MORE COMPLICATED MONDAY AND TUESDAY WITH AN UPPER LOW SLIDING INTO THE PACIFIC NW STATES MONDAY AND TOWARD THE ROCKIES ON TUE. THE GFS AND CANADIAN MODELS ARE POINTING AT THIS WHILE THE ECMWF KEEPS THE UPPER LOW OVER THE PACIFIC NW STATES THROUGH TUESDAY. FOR NOW HAVE A CHANCE OF SNOW FOR THE NW MTS AND A SLIGHT CHANCE OF SNOW FOR THE NORTHERN ZONES. PLENTY OF TIME TO WATCH HOW THIS UNFOLDS. TEMPS WILL BE SEASONAL THROUGH THE EXTENDED PERIOD WITH LITTLE DAY TO DAY CHANGE IN HIGHS AND LOWS. EXPECT HIGHS IN THE 20S AND 30S WITH LOWS IN THE SINGLE DIGITS AND TEENS...AND SOME BELOW ZERO LOWS IN THE SNOW COVERED BASINS. && .AVIATION... WEST OF THE DIVIDE...EXPECT SOME LOW CLOUDS...POSSIBLY IN THE MVFR CATEGORY IN STAR VALLEY...KAFO...AND JACKSON HOLE...KJAC...IN THE MORNING...BUT CLOUDS WILL LOWER DURING THE AFTERNOON AS A WEAK STORM SYSTEM MOVES INTO WESTERN WYOMING. PREVAILING MVFR CEILINGS AND OCCASIONAL IFR VISIBILITIES ARE EXPECTED BY MID-LATE AFTERNOON. THE UPPER GREEN RIVER BASIN COULD SEE PATCHY FOG DURING THE MORNING WITH MVFR/IFR CONDITIONS FOR KBPI/KPNA THROUGH ABOUT 16Z. VFR IS THEN EXPECTED IN THAT AREA DURING THE AFTERNOON AND EVENING...BEFORE SOME LOW CLOUDS COULD AFFECT KBPI/KPNA AFTER 06Z TONIGHT. VFR ARE EXPECTED OVER THE SOUTH AND EAST OF THE DIVIDE THROUGH TONIGHT...WITH CONSIDERABLE MID/HIGH LEVEL CLOUDINESS...ESPECIALLY DURING THE MORNING HOURS. STRONG SOUTHWEST WINDS ARE EXPECTED FROM SOUTH PASS...EAST TO KCPR WITH SUSTAINED WINDS INCREASING TO 25 TO 40 KTS WITH SOME GUSTS AROUND 55 KTS BY 18Z. THESE WINDS ARE EXPECTED TO DECREASE GRADUALLY DURING THE EVENING HOURS. SOME STRONG WESTERLY WINDS ARE ALSO EXPECTED OVER THE ABSAROKA MTS...AND ADJACENT LOWER ELEVATIONS OF THE CODY FOOTHILLS. HOWEVER...THESE WINDS ARE EXPECTED TO HAVE A MINIMAL IMPACT AT THE KCOD TERMINAL. && .FIRE WEATHER... STRONG WIND WILL DEVELOP OVER THE GREEN MOUNTAINS AND RATTLESNAKE RANGE THIS MORNING AND CONTINUE THROUGH THE EVENING HOURS. WIND OF AROUND 40 MPH IS EXPECTED...WITH GUSTS UP TO 60 MPH. ADDITIONALLY...STRONG WIND IS EXPECTED TO DEVELOP OVER THE ABSAROKA MOUNTAINS AND CODY FOOTHILLS THIS MORNING AND CONTINUE THROUGH WEDNESDAY MORNING. THE LATTER LOCATION HAS THE POTENTIAL TO BE A SIGNIFICANT WIND EVENT...WITH THE POTENTIAL OF GUSTS TO 80 MPH OVER THE FOOTHILLS NEAR THE EASTERN SLOPES OF THE ABSAROKA MOUNTAINS. OTHERWISE...LIGHT SNOWFALL WILL CONTINUE TO FALL OVER THE WESTERN MOUNTAINS AND VALLEYS FOR THE NEXT FEW DAYS. ACCUMULATIONS OVER MOUNTAIN LOCATIONS ARE EXPECTED TO BE BETWEEN 3 AND 5 INCHES BY WEDNESDAY EVENING...THOUGH SOME AREAS MAY SEE LOCALLY HEAVIER SNOWFALL AMOUNTS. THE VALLEYS WILL SEE SNOWFALL OF 1 TO 2 INCHES. TEMPERATURES WILL CONTINUE TO WARM OVER THE NEXT COUPLE OF DAYS...WITH SOME LIGHT SHOWER ACTIVITY DEVELOPING OVER THE EASTERN PORTION OF THE AREA BY THURSDAY. && .RIW WATCHES/WARNINGS/ADVISORIES... HIGH WIND WARNING UNTIL 5 AM MST WEDNESDAY FOR WYZ002-003. HIGH WIND WARNING UNTIL 11 PM MST THIS EVENING FOR WYZ019. && SHORT TERM...BRANHAM LONG TERM...AR AVIATION...WM FIRE WEATHER...BRANHAM
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 233 AM MST TUE DEC 15 2009 WYZ001>020-022>030-160700- 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- 233 AM MST TUE DEC 15 2009 ...HIGH WIND WARNING IN EFFECT FOR PORTIONS OF NORTH CENTRAL AND CENTRAL WYOMING THROUGH TONIGHT... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT VERY STRONG WIND WILL DEVELOP OVER THE GREEN MOUNTAINS AND RATTLESNAKE RANGE THIS MORNING AND WILL CONTINUE THROUGH THE EVENING HOURS. WIND OF AROUND 40 MPH WITH GUSTS TO 60 MPH WILL BE POSSIBLE TODAY...ESPECIALLY DURING THE LATE MORNING AND AFTERNOON HOURS. ADDITIONALLY...VERY STRONG TO POTENTIALLY DAMAGING WIND WILL DEVELOP OVER THE EASTERN SLOPES OF THE ABSAROKA MOUNTAINS AND IMPACT THE WESTERN THIRD OF THE CODY FOOTHILLS TODAY. THERE WILL BE ANOTHER PULSE OF INCREASED WIND OVER THESE AREAS OVERNIGHT. BREEZY WIND OF 25 TO 35 MPH WITH GUSTS TO AROUND 50 MPH WILL ALSO BE POSSIBLE OVER THE LOWER ELEVATIONS OF NATRONA COUNTY...INCLUDING THE CASPER AREA. THIS INCREASED SOUTHWESTERLY WIND WILL BRING HAZARDOUS CROSS WINDS ACROSS INTERSTATE 25 AND WILL IMPACT TRAVEL FOR THOSE TRAVELING WITH HIGH PROFILE VEHICLES THIS AFTERNOON. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY STRONG WIND OVER THE ABSAROKA MOUNTAINS AND CODY FOOTHILLS WILL CONTINUE INTO THE MORNING HOURS OF WEDNESDAY BEFORE WEAKENING. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ENCOURAGED TO REPORT WIND OVER 40 MPH OR WIND GUSTS OVER 60 MPH TODAY AND TONIGHT. TEAM RIVERTON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 241 AM MST TUE DEC 15 2009 WYZ020-152300- NATRONA COUNTY LOWER ELEVATIONS- 241 AM MST TUE DEC 15 2009 ...WINDY CONDITIONS POSSIBLE TODAY... SOUTHWESTERLY WIND OF 25 TO 35 MPH WITH GUSTS UP TO 50 MPH WILL BE POSSIBLE ACROSS THE LOWER ELEVATIONS OF NATRONA COUNTY THIS AFTERNOON. THESE WINDY CONDITIONS WILL CAUSE POTENTIALLY HAZARDOUS CROSS WINDS ACROSS INTERSTATE 25. PERSONS TRAVELING...ESPECIALLY THOSE IN HIGH PROFILE VEHICLES...SHOULD CHECK CURRENT CONDITIONS BEFORE TRAVELING TODAY. BRANHAM
The national radar mosaic for the moment the first event began.
3 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, December 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: 199996, 199995, 199994.