A significant surface pressure gradient allowed strong southwest wind to prevail across central Wyoming. Gusty wind along Wyoming Boulevard in Casper toppled a semi-truck.
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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 significant surface pressure gradient allowed strong southwest wind to prevail across central Wyoming. Gusty wind along Wyoming Boulevard in Casper toppled a semi-truck. Sustained wind of 46 mph was measured along U.S. Highway 287 near Sweetwater Station.
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 8, 3:20 AM MST, 6 hours 20 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 320 AM MST THU JAN 8 2009 .SHORT TERM...TODAY THROUGH SATURDAY NIGHT MOIST SHORT-WAVE TROUGH AXIS NEAR THE WASHINGTON COASTLINE EARLY THIS MORNING. THIS FEATURE WILL BEGIN TO SPLIT AS IT COMES ASHORE TODAY...WITH A PORTION OF THE WAVE DIGGING SOUTHWARD INTO NORTHERN NEVADA WITH ANOTHER PORTION MOVING EASTWARD THROUGH MONTANA. MID TO UPPER LEVEL DRY SLOT EXPECTED TO MOVE OVER WESTERN WYOMING AROUND MIDDAY WITH SHALLOW WEAK ISENTROPIC UPGLIDE CONTINUING FROM MOUNTAIN TOP LEVEL DOWNWARD OVER THE FAR NORTHWEST. THIS SHOULD BE ENOUGH TO KEEP AREAS OF LIGHT SNOW GOING OVER THE TETONS...GROS VENTRES AND YELLOWSTONE PARK WITH SOME PEAKS AT BLUE SKY. THE STRONG PRESSURE GRADIENT OVER THE STATE WILL KEEP THE ATMOSPHERE RELATIVELY WELL MIXED THIS MORNING WITH MOST LOCATIONS MIXING TO APPROXIMATELY H7 DURING THE AFTERNOON. LOW TO MID 50S EXPECTED IN THE LOWER ELEVATIONS OF THE BIGHORN AND WIND RIVER BASINS AS WELL AS IN JOHNSON AND NATRONA COUNTIES. ASSOCIATED SURFACE COLD FRONT WILL MOVE THROUGH THE FAR WEST DURING THE LATE AFTERNOON...BRINGING AN END TO THE LIGHT UPGLIDE SNOW/RAIN-SNOW MIX OVER THE WEST. SCATTERED TO NUMEROUS MODERATE SNOW SHOWERS WILL REPLACE THE LIGHT SNOW AND RAIN OVER THE FAR WEST ALONG AND BEHIND THE COLD FRONT...WITH BRIEF HEAVY SNOW POSSIBLE IN THE HEAVIER SHOWERS. SNOWFALL ACCUMULATIONS MARGINAL FOR A WINTER WEATHER ADVISORY...WITH MORE OF A CONVECTIVE TYPE EVENT AFTER APPROX. 3 TO 5 HOURS OF LIGHT SNOW UNDER WEAK UPGLIDE. DECIDED TO FORGO ANY HIGHLIGHTS WITH THE BRIEF AND SHALLOW (DRY SLOT ABOVE) WARM SECTOR SNOWFALL WITH MOST ACCUMULATIONS OCCURRING ALONG AND BEHIND THE FRONT LESS LIKELY TO BE WIDESPREAD AND BRING THE HIGHEST SNOW AMOUNTS TO THE HIGHER WESTERN SLOPES DUE TO OROGRAPHIC EFFECTS. ALSO...TEMPS ARE TOO WARM IN THE WESTERN VALLEYS BEFORE SUNSET TO SUPPORT ACCUMULATING SNOW. HIGH WIND EXPECTED ONCE AGAIN FOR THE WIND CORRIDOR FROM JUST NORTHEAST OF ROCK SPRINGS TO CASPER. STRONG SURFACE PRESSURE GRADIENT SETTING UP AND COMBINING WITH A 50-60KT SPEED MAX AT H7 TO PRODUCE GOOD POTENTIAL FOR HIGH WIND. ISSUED A HIGH WIND WATCH FOR THIS AFTERNOON THROUGH THE EARLY EVENING FOR VERY STRONG WEST TO SOUTHWEST WIND BEGINNING AROUND MIDDAY AND PEAKING DURING THE AFTERNOON. SURFACE HIGH PRESSURE ASSOCIATED WITH THE ABOVE MENTIONED PORTION OF THE MONTANA TROUGH WILL NOSE SOUTHWARD INTO JOHNSON AND NATRONA COUNTY DURING THE DAY FRIDAY. THE FRONTOGENTIC FORCING WITH THIS FEATURE WILL PROVIDE A QUICK BURST OF SNOW TO THE BIGHORN MOUNTAINS...FAR NORTHEASTERN BIGHORN BASIN AND JOHNSON COUNTY FRIDAY MORNING. THE SNOW WILL MOVE SOUTH INTO NATRONA COUNTY FRIDAY AFTERNOON. ECMWF SHOWING SOME SIGNS OF NOSING THE SURFACE HIGH AND MESO-SCALE FORCING SOUTHWARD INTO THE SOUTHERN BIGHORN BASIN AND WIND RIVER BASIN...BUT FOR NOW IT APPEARS THESE AREAS LIKELY TO EXPERIENCE FLURRIES OR A DUSTING AT BEST. DRY NORTHWEST FLOW ALOFT DEVELOPS OVER THE STATE SATURDAY AND SATURDAY NIGHT. LATEST GFS AND ECMWF HINTING AT WEAK FAST MOVING SHORT-WAVE TROUGHS TRACKING THROUGH THE FLOW WHICH MAY BRING CLOUDS AND FLURRIES TO THE NORTH SATURDAY NIGHT. .LONG TERM...SUNDAY THROUGH THURSDAY MODELS IN GOOD AGREEMENT WITH NORTHWEST FLOW CONTINUING OVER THE STATE ON SUNDAY. SHORTWAVE ZIPPING THROUGH SUNDAY AFTERNOON AND NIGHT WILL TRIGGER INCREASING CHANCE OF PRECIPITATION ACROSS THE EASTERN THIRD OF THE FORECAST AREA. NOSE OF VIGOROUS 150KT+ 300MB JET WILL AID LIFT ACROSS THIS AREA SUNDAY EVENING. RIDGE THEN BEGINS TO BUILD OVER THE EASTERN PACIFIC ON MONDAY AND TUESDAY WITH THE DOMINANT FEATURE BECOMING THE STRONG HUDSON BAY LOW. THIS LOW WILL IMPACT WEATHER FOR MUCH OF THE U.S. EAST OF THE ROCKIES DURING MOST OF NEXT WEEK. RIDGE/TROUGH PATTERN ACROSS THE U.S. AMPLIFIES EARLY IN THE WEEK LEAVING FORECAST AREA IN NORTHWEST FLOW. RELATIVELY MILD TEMPERATURES AND LIGHT SNOW ACROSS THE NORTHERN MOUNTAINS TO PREVAIL THESE DAYS IN PESKY NORTHWEST FLOW. TIMING SHORTWAVES ACROSS THE AREA WOULD BE DIFFICULT AT THIS TIME RANGE. ALSO...THIS COULD BE A WINDY PERIOD FOR NORTHWEST WIND FAVORED LOCATIONS OF THE BIG HORN BASIN AND NORTHERN JOHNSON COUNTY. MODELS THEN BEGIN TO DIVERGE BY MIDWEEK AS TO WHETHER HUDSON BAY LOW CAN SLIDE ARCTIC AIR INTO THE AREA THROUGH THE BACKDOOR. EVEN THE DIFFERENCE IN THE SOLUTIONS OFFERED BY THE 12Z/WED AND 00Z/THU RUNS OF THE ECMWF DIFFER GREATLY ON THE EXTENT OF POSSIBLE ARCTIC INTRUSION INTO OUR AREA. GFS KEEPS US MILD DURING THIS PERIOD WITH RIDGE EXTENDING FAR ENOUGH INLAND TO KEEP THE COLDER AIR TO OUR EAST. 12Z/WED ECMWF SOLUTION HAD A SHORTWAVE TOPPING THE RIDGE AND DIGGING SOUTH ACROSS WYOMING WHICH WOULD LIKELY BRING ARCTIC AIR TO LOCATIONS EAST OF THE DIVIDE. HOWEVER...00Z/THU RUN KEEPS THIS FEATURE TO OUR EAST. NONETHELESS...THICKNESSES AND 700MB TEMPS INDICATE COLDER TEMPS FOR JOHNSON AND NATRONA COUNTIES ON THURSDAY AND THURSDAY NIGHT AND TO A LESSER EXTENT THE WIND RIVER AND BIG HORN BASINS. AHEAD OF THIS FEATURE...WEDNESDAY TEMPS WILL REMAIN RELATIVELY MILD FOR JANUARY. WOULD PREFER TO SEE MORE RUN-TO-RUN CONSISTENCY BEFORE BITING OFF EITHER WAY ON THURSDAY FORECAST. INTRUSION WOULD ALSO GENERATE SOME LIGHT PRECIPITATION IN NORTHERLY FLOW AND HAVE ADJUSTED JOHNSON/NATRONA CHANCES ACCORDINGLY. && .AVIATION... WEST AND CENTRAL WYOMING WILL BE MOSTLY IN THE DRY WARM SECTOR AHEAD OF AN APPROACHING COLD FRONT TODAY WITH STRONG SOUTHWEST WIND 30 TO 40KT GUSTING NEAR 50KT DEVELOPING BETWEEN KRKS-KCPR. AREAS OF LLWS WILL BE ENCOUNTERED ALONG THE EAST SLOPES OF THE DIVIDE FROM KCOD- KLND WITH 8-10KFT MSL WINDS WSW AT 40-50KT. LOCAL MFVR CLOUD DECKS WITH -SN...MOUNTAINS PARTIALLY OBSCURED WILL BE ENCOUNTERED VCNTY KJAC AND THE NORTHWEST MOUNTAINS THROUGH 21Z WITH CONDITIONS DETERIORATING AFTERWORDS. WIDESPREAD MVFR WITH AREAS OF IFR CONDITIONS...MOUNTAINS OBSCURED...WILL BE ENCOUNTERED ALONG KPNA-KJAC ROUTES AND OVER THE WESTERN MOUNTAINS AFTER 00Z FRIDAY. A COLD FRONT WILL MOVE ACROSS THE STATE THURSDAY NIGHT RESULTING IN AREAS OF MVFR CONDITIONS IN LIGHT SNOW SPREADING EAST OF THE DIVIDE 03Z-12Z FRIDAY. && .FIRE WEATHER... HIGH WIND IS EXPECTED ONCE AGAIN OVER PORTIONS OF CENTRAL WYOMING FROM JUST NORTHEAST OF ROCK SPRINGS TO CASPER. MUCH ABOVE NORMAL TEMPERATURES WILL OCCUR EAST OF THE DIVIDE. AREAS OF LIGHT SNOW WILL CONTINUE OVER THE WESTERN MOUNTAINS TODAY AHEAD OF PACIFIC COLD FRONT. THE FRONT WILL MOVE FROM NORTHWEST TO SOUTHEAST THROUGH THE STATE TONIGHT. SCATTERED TO NUMEROUS SNOW SHOWERS WILL ACCOMPANY THE FRONT AS IT MOVES THROUGH WESTERN AND NORTHERN WYOMING TONIGHT AND FRIDAY MORNING. HIGH PRESSURE BUILDS OVER THE DISTRICT SATURDAY. && .RIW WATCHES/WARNINGS/ADVISORIES... HIGH WIND WATCH FROM 11 AM MST THURSDAY THROUGH THURSDAY AFTERNOON FOR WYZ019-020. && SHORT TERM...CHURCH LONG TERM...CNJ AVIATION...AEM FIRE WEATHER...CHURCH
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 928 AM MST THU JAN 8 2009 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- 928 AM MST THU JAN 8 2009 ...HIGH WIND WARNING IN EFFECT FOR THE GREEN AND RATTLESNAKE MOUNTAINS...AND LOWER ELEVATIONS OF NATRONA COUNTY THROUGH 6 PM THIS EVENING... THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN AND CENTRAL WYOMING. .DAY ONE...TODAY AND TONIGHT STRONG SOUTHWEST WINDS OF 35 TO 45 MPH WITH GUSTS TO 65 MPH ARE EXPECTED FROM SOUTH PASS...OVER BEAVER RIM AND THROUGH THE SOUTH SIDE OF CASPER THROUGH 6 PM TODAY. THE STRONGEST WINDS WILL OCCUR BETWEEN 2 PM AND 5 PM THIS AFTERNOON. SEE THE HIGH WIND WARNING PRODUCT FOR MORE INFORMATION. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ASKED TO REPORT ANY RECORDED STRONG WIND GUSTS...WIND DAMAGE OR SNOW ACCUMULATION FROM TODAY. THANK YOU. TEAM RIVERTON
The national radar mosaic for the moment the first event began.
2 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: 142210, 142209.