A tightening surface pressure gradient and unseasonably warm temperatures allowed for strong west-southwest wind to mix to the surface. S.
Every event with a place to put it; 1 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.
A tightening surface pressure gradient and unseasonably warm temperatures allowed for strong west-southwest wind to mix to the surface. The wind was strongest along U.S. Highway 287 over Beaver Rim where a peak wind of 61 mph was measured. Sustained wind over 40 mph frequently occurred during the very early afternoon hours.
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 Nov 6, 2:39 AM MST, 9 hours 52 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RIVERTON WY 239 AM MST FRI NOV 6 2009 .SHORT TERM...TODAY THROUGH SUNDAY NIGHT STRONG JET STREAM APPROACHING THE REGION THIS MORNING FROM THE PAC NW. THIS TO BRING STRONG WIND TO PORTIONS OF THE AREA TODAY AS WELL AS SOME SNOW SHOWERS TO THE NORTHWEST. WINDS WILL BE THE BIGGEST IMPACT FROM THIS SYSTEM...ESPECIALLY TO NATRONA AND SOUTHEAST FREMONT COUNTIES AS WELL AS TO THE CODY FOOTHILLS...ABSAROKAS AND EASTERN WIND RIVERS. WILL HAVE AN 8-10MB SOUTHWEST TO WEST GRADIENT ACROSS SWEETWATER TO CAMPBELL COUNTIES THIS MORNING. ALSO HAVE H7 WINDS OF 40-50KTS AS WELL. WITH THIS...SHOULD SEE WIND SPEEDS OF 25 TO 35 MPH WITH GUSTS TO 55 MPH WITH LOCAL GUSTS EXCEEDING 60 MPH OVER SOUTHEAST FREMONT AND NATRONA COUNTIES. THE GRADIENT WILL BE MORE WEST ALONG THE CODY FOOTHILLS WITH 40-50KT MOUNTAIN TOP WIND. SIMILAR SPEEDS EXPECTED ALONG THE CODY FOOTHILLS. NO LONGER EXPECTING WIDESPREAD HIGH WINDS OVER THESE AREAS TODAY...SO HAVE DROPPED THE HIGH WIND WATCH THAT WAS IN EFFECT FOR TODAY. THE WINDS WILL BEGIN TO SLACKEN THIS EVENING REMAINING WINDY THROUGH SATURDAY EVENING BEFORE DIMINISHING SUNDAY MORNING AS RIDGE BEGINS TO BUILD IN. MOST PLACES TO BE BREEZY TO WINDY TODAY...THEN AGAIN SATURDAY. MOISTURE WILL MOVE INTO THE NORTHWEST TODAY AND WITH THE JET APPROACHING EXPECT SNOW SHOWERS THERE. LIS DOWN TO +2C OR SO THIS AFTERNOON. THIS ZONAL FLOW PATTERN WILL KEEP A STEADY BUT LIMITED SUPPLY OF MOISTURE FEEDING INTO THE NORTHWEST THROUGH SATURDAY EVENING. NOT MUCH UPPER DYNAMICS TO WORK WITH BUT THERE IS OROGRAPHIC LIFT WITH THE STRONG FLOW AS WELL AS SOME INSTABILITY TO WORK WITH...SO EXPECT THE SNOW SHOWERS TO CONTINUE THROUGH SATURDAY EVENING...BEFORE ENDING SUNDAY MORNING. MUCH COOLER AIR WILL WORK INTO THE WEST THIS MORNING AND INTO THE EAST LATER THIS AFTERNOON AND EVENING. WILL STILL SEE SOME VERY MILD...ABOVE NORMAL TEMPS IN THE EAST TODAY...THEN BECOMING MORE SEASONABLE FOR SATURDAY AND SUNDAY. SUNDAY WILL SEE LINGERING CLOUDS IN THE WEST SLOWLY DISSIPATING IN THE AFTERNOON AND OVERNIGHT. THE REMAINDER OF THE AREA LOOKS TO BE A NICE DAY FOR EARLY NOVEMBER. .LONG TERM...MONDAY THROUGH FRIDAY FAST PROGRESSIVE ZONAL FLOW WITH A BROAD FLAT TROUGH WILL EXTEND FROM THE EASTERN PACIFIC ACROSS THE PACIFIC NORTHWEST...THE NORTHERN GREAT BASIN AND ACROSS WYOMING INTO THE NORTHERN AND CENTRAL PLAINS. A SERIES OF FAST MOVING SHORT WAVE TROUGHS WILL BRING PACIFIC MOISTURE INTO THE WESTERN MOUNTAINS BRINGING LOCAL SHOWERS TO THE WESTERN MOUNTAINS, THIS WILL BRING BREEZY AREAS EAST OF THE CONTINENTAL DIVIDE AND ACROSS THE SOUTH. MONDAY AND MONDAY NIGHT A WEAK SHORT WAVE RIDGE WILL BE OVER THE AREA WITH A BREAK IN THE PACIFIC MOISTURE. TEMPERATURES WILL BE COOLER AT NIGHT WITH DRY COOLER AIR OVER THE AREA. TUESDAY THE FLOW BACKS AHEAD OF A DEEPENING PACIFIC TROUGH. WIND SHOULD PICK UP AND TEMPERATURES SHOULD RISE. PACIFIC MOISTURE REMAINS TO THE WEST UNTIL WEDNESDAY AS THE PACIFIC TROUGH MOVES INLAND. PRECIPITATION... MAINLY SNOW WITH SOME RAIN IN THE VALLEYS WILL MOVE INTO THE WEST, WINDS WILL PICK UP EAST OF THE DIVIDE. THURSDAY THE TROUGH WILL PASS TROUGH THEN FOLLOWED BY A CANADIAN TROUGH. THIS WILL SPREAD THE THREAT OF PRECIPITATION EAST OF THE DIVIDE. MODELS HAVE BEEN INCONSISTENT WITH THE STRENGTH OF THE CLIPPER TROUGH AND THE AMOUNT OF PRECIPITATION WITH IT. FORECAST RATHER CONSERVATIVE AT THIS TIME DUE TO MODEL FLIP FLOPS. SHOULD BE COLDER AS ZONAL FLOW BUCKLES WITH A DEVELOPING LONG WAVE TROUGH OVER THE WEST AND THE FLOW SHIFTING FROM THE PACIFIC TO CANADA. THERE IS CONSIDERABLE MODEL SPREAD WITH THE FEATURES WITHIN THE LONG WAVE TROUGH. THERE IS POTENTIAL FOR A MUCH MORE SIGNIFICANT SPREAD OF PRECIPITATION...JUST AS THERE IS POTENTIAL FOR THE ZONAL NATURE OF THE FLOW TO HOLD OUT WITH LESS DIGGING OF THE MEAN TROUGH WITH THE PASSAGE OF A SERIES OF SHORT WAVE TROUGHS. THE MODELS A FAR APART TO THE NORTH...ACROSS CANADA AND TO THE WEST ACROSS THE EASTERN PACIFIC AND GULF OF ALASKA BY FRIDAY. THE MAIN STORY THURSDAY AND FRIDAY WILL BE COLDER AND MAYBE SNOW SHOWERS...OR MORE ORGANIZED PRECIPITATION ACROSS THE NORTH AND EAST. THIS MAKES FOR LOW CONFIDENCE IN THE EXTENDED AFTER WEDNESDAY. && .AVIATION... VFR CONDITIONS WILL PREVAIL ACROSS THE AREA TODAY AND TONIGHT OVER MOST OF THE AREA WITH SOME LOCAL MVFR CONDITIONS AND OCCASIONAL MOUNTAIN OBSCURATIONS VCNTY AND NORTH OF A KJAC-KCOD LINE IN SCATTERED RAIN AND SNOW SHOWERS...SNOW LEVELS BETWEEN 7K-8KFT. A STRONG SOUTHWEST FLOW WILL PREVAIL ACROSS MUCH OF CENTRAL WYOMING WITH AREAS OF LLWS ALONG THE EASTERN FOOTHILLS VCNTY KLND-KCOD LINE. AREAS OF SFC SW WINDS AT 25-35KTS WITH GUSTS 45KTS WILL BE ENCOUNTERED BETWEEN KRKS-KCPR THROUGH THE DAY. SFC WINDS ACROSS THE AREA WILL DIMINISH WITH SUNSET OR AFTER 00Z SAT. && .FIRE WEATHER... STRONG WINDS EXPECTED TODAY OVER THE CODY FOOTHILLS...ABSAROKAS... EASTERN WIND RIVERS...NATRONA AND SOUTHEAST FREMONT COUNTIES. SOUTHWEST TO WEST WINDS OF 25 TO 35 MPH WITH GUSTS TO 55 MPH ARE EXPECTED...WITH HIGHER WINDS IN THE MOUNTAINS. MOST OTHER AREAS WILL BE WINDY TODAY AS WELL. THE WINDS WILL SLACKEN TONIGHT BUT CONTINUE THROUGH SUNDAY MORNING. NUMEROUS SNOW SHOWERS ARE ALSO EXPECTED IN THE NORTHWEST TODAY THROUGH SUNDAY MORNING...PRODUCING ACCUMULATIONS OF UP TO 4 INCHES. IT WILL REMAIN MILD TODAY OVER THE EAST...WITH COOLING TEMPERATURES IN THE WEST. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...TWB LONG TERM...C.BAKER AVIATION...AEM FIRE WEATHER...TWB
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE RIVERTON WY 501 AM MST FRI NOV 6 2009 WYZ001>020-022>030-071201- 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- 501 AM MST FRI NOV 6 2009 .DAY ONE...TODAY AND TONIGHT STRONG SOUTHWEST TO WEST WINDS OF 25 TO 35 MPH...WITH GUSTS AROUND 55 MPH ARE EXPECTED ALONG THE CODY FOOTHILLS...AS WELL AS OVER SOUTHEAST FREMONT AND MUCH OF NATRONA COUNTIES...INCLUDING CASPER FROM LATE TONIGHT THROUGH THE DAY ON FRIDAY. OTHER AREAS SUCH AS THE EASTERN ABSAROKA MOUNTAINS AND EASTERN WIND RIVER MOUNTAINS WILL ALSO HAVE STRONG WINDS TONIGHT AND FRIDAY. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY SOUTHWEST TO WEST WINDS WILL CONTINUE SATURDAY OVER THE SAME AREAS AS TODAY...WITH SPEEDS OF 20 TO 30 MPH WITH GUSTS TO 40 MPH. .SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ASKED TO REPORT WIND SPEEDS GREATER THAN 40 MPH TONIGHT AND FRIDAY. THANK YOU. TEAM RIVERTON
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE RIVERTON WY 1126 AM MST FRI NOV 6 2009 WYZ002-003-070100- ABSAROKA MOUNTAINS-CODY FOOTHILLS- 1126 AM MST FRI NOV 6 2009 ...STRONG WINDS WILL CONTINUE ALONG THE CODY FOOTHILLS AND THE EAST SLOPE OF THE ABSAROKA MOUNTAINS THROUGH THE EARLY EVENING... WEST WIND OF 25 TO 35 MPH WITH GUSTS TO 55 MPH ARE EXPECTED ALONG THE CODY FOOTHILLS THIS AFTERNOON AND EARLY EVENING...INCLUDING CODY AND CLARK. HIGHER WIND IS POSSIBLE IN THE MOUNTAINS...ESPECIALLY OVER CHIEF JOSEPH PASS. THE WIND WILL BEGIN TO TAPER OFF DURING THE EARLY EVENING. TRAVELERS ALONG HIGHWAY 120 SHOULD BE PREPARED FOR STRONG WIND GUSTS. WYZ019-020-022-070100- CASPER MOUNTAIN-GREEN MOUNTAINS AND RATTLESNAKE RANGE- NATRONA COUNTY LOWER ELEVATIONS- 1126 AM MST FRI NOV 6 2009 SOUTHWEST WIND OF 25 TO 35 MPH WITH GUSTS TO 55 MPH ARE WILL CONTINUE THIS AFTERNOON THROUGH EARLY THIS EVENING. LOCALLY HIGHER WIND IS POSSIBLE ALONG OUTER DRIVE ON THE SOUTH SIDE OF CASPER. THE WIND WILL GRADUALLY TAPER OFF DURING THE EARLY EVENING. TRAVELERS ON INTERSTATE 25 AND HIGHWAYS 20...26...220 AND 287 SHOULD BE PREPARED FOR STRONG WIND GUSTS. WYZ015-070100- WIND RIVER MOUNTAINS EAST- 1126 AM MST FRI NOV 6 2009 SOUTHWEST WIND OF 30 TO 40 MPH WITH GUSTS TO 60 MPH WILL CONTINUE THIS AFTERNOON AND EARLY EVENING ALONG THE EAST SLOPES OF THE WIND RIVER MOUNTAINS...INCLUDING SOUTH PASS. THE STRONG WIND WILL GRADUALLY TAPER OFF DURING THE EARLY EVENING. TRAVELERS ON SOUTH PASS...HIGHWAY 28 SHOULD BE PREPARED FOR STRONG WIND GUSTS. TWB
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, November 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: 196998.