Microburst from weak shower.
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 CYS wrote it up.
Microburst from weak shower.
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 Cheyenne, WY wrote its last area forecast discussion before the first event at May 11, 1:42 PM MST, 3 hours 35 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 242 PM MDT FRI MAY 11 2007 .SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT... A SUMMER LIKE PATTERN SETTING UP THROUGH THE PERIOD AS RIDGE AXIS HOVERS ACROSS THE CO/NM AREAS. WEAK MID LEVEL MOISTURE EMBEDDED WITHIN THE FLOW WILL ROTATE ALONG THE NORTH SIDE OF THE UPPER RIDGE. AS A RESULT HIGH-BASED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO DEVELOP THIS AFTERNOON AND EVENING. AT THE SURFACE...AN AREA OF SURFACE CONVERGENCE WILL SET UP ACROSS NORTHERN ZONES BY LATE THIS AFTERNOON AND THIS EVENING. THIS WILL PROVIDE ANOTHER FOCAL POINT FOR CONVECTIVE INITIATION. ALTHOUGH INSTABILITY VALUES ARE FAVORABLE FOR THUNDERSTORM DEVELOPMENT...A WARM MID LAYER AT AROUND 700MB WILL PRECLUDE ANY SIGNIFICANT DEVELOPMENT. HOWEVER...IN AREAS WHERE THE PARCEL CAN BE LIFTED AT OR ABOVE THAT LEVEL...ISOLATED SINGLE CELL PULSE STORMS WILL DEVELOP. ALSO CAN NOT RULE OUT A ROGUE CELL THAT IS ABLE TO ROLL OFF ONTO THE PLAINS FOR A WHILE. OVERALL...EXPECT COVERAGE TO BE LIMITED. A FEW STORMS MAY PRODUCE BRIEF HEAVY RAIN AND THUNDERSTORM WINDS TO 40 MPH. CONVECTION WILL BE DRIVEN PRIMARILY BY INSOLATION...SO ANTICIPATE RAPID DISSIPATION AROUND OR SHORTLY AFTER SUNSET. FLOW WILL BEGIN TO BACK TO THE SOUTHWEST ON SATURDAY AS THE RIDGE BEGINS TO BREAK DOWN AND SHIFT EAST. ANOTHER ROUND OF HIGH-BASED AFTERNOON AND EVENING STORMS WILL BE POSSIBLE ONCE AGAIN ON SATURDAY AFTERNOON. COVERAGE WILL BE LIMITED. TEMPERATURES WILL CONTINUE TO WARM AS 700MB TEMPERATURES WARM TO 11 TO 12C. THIS WILL YIELD LOW 80S AT 5 KFT...WITH LOW 90S ANTICIPATED ACROSS LOWER ELEVATIONS OF THE PANHANDLE...AND ALONG THE NORTH PLATTE OF SE WY. .LONG TERM...SUNDAY THROUGH FRIDAY... THE BACK SIDE OF THE UPPER RIDGE WILL BE SHIFTING OVER THE FORECAST AREA EXPOSING MID LEVEL MOISTURE FROM THE SW. THUNDERSTORMS...SOME DRY...WILL FORM IN THE PRE-FRONTAL INSTABILITY SUNDAY AFTERNOON...SO A FIRE WEATHER CONCERN MAY MATERIALIZE GIVEN THE HEAT UNDER THE RIDGE. MODELS FAIRLY CONGRUENT SHOWING A SIMILAR FROPA DURING THE DAY MONDAY...BUT THE EURO IS SEVERAL HOURS FASTER...WITH THE GFS THE SLOWEST AT THIS TIME...SHOWING MONDAY EVENING. TEMPERATURES WILL TAKE A 20 DEGREE HIT INTO MONDAY WITH POST-FRONTAL UPSLOPE AND ASSOCIATED RAIN/THUNDER CHANCES PERSISTING THROUGH EARLY TUESDAY. THE REST OF THE WEEK WILL BE MARKED BY THE RIDGE TRYING TO REESTABLISH ITSELF OVER THE REGION. TEMPERATURES SHOULD RISE EACH DAY WITH ISOLATED CONVECTION EACH AFTERNOON. && .AVIATION... VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD. ISOLATED LATE AFTERNOON AND EARLY EVENING CONVECTION WILL SPARK IN THE VICINITY OF THE MOUNTAINS AND ACROSS EAST CENTRAL WYOMING. && .FIRE WEATHER... NON-CRITICAL FUELS ARE IN PLACE CURRENTLY DURING GREEN-UP. NONETHELESS...SIGNIFICANT DRYING IS OCCURRING PARTICULARLY ACROSS WRN ZONES WHERE TEEN AND LOW 20S DEWPOINTS WERE COMMON. THIS WILL CONTINUE TO BE THE TREND OVER THE NEXT SEVERAL DAYS. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...NONE. NE...NONE. && SHORT TERM/AVIATION...HAHN LONG TERM....SOWKO
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE CHEYENNE WY 1049 AM MDT FRI MAY 11 2007 NEZ001>003-WYZ059-060-063>069-121700- SIOUX-DAWES-BOX BUTTE-CONVERSE-NIOBRARA-SNOWY RANGE- NORTH LARAMIE RANGE-LARAMIE VALLEY-LARAMIE RANGE-PLATTE-GOSHEN- CHEYENNE FOOTHILLS- 1049 AM MDT FRI MAY 11 2007 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WESTERN NEBRASKA PANHANDLE AND SOUTHEAST WYOMING. .DAY ONE...TODAY AND TONIGHT ISOLATED WEAK THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON INTO EARLY THIS EVENING MAINLY OVER THE MOUNTAINS AND NORTH OF HIGHWAY 26. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY THERE IS A CHANCE FOR MAINLY AFTERNOON AND EVENING THUNDERSTORMS SATURDAY THROUGH MONDAY...AND AGAIN THURSDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT. && THIS PRODUCT...ALONG WITH OTHER WEATHER...HYDROLOGIC...AND CLIMATE INFORMATION IS AVAILABLE ON THE WEB AT... HTTP://WEATHER.GOV/CHEYENNE NEZ019>021-054-055-WYZ061-062-070-121700- SCOTTS BLUFF-BANNER-MORRILL-KIMBALL-CHEYENNE-SOUTHWEST CARBON- NORTH CARBON-PINE BLUFFS- 1049 AM MDT FRI MAY 11 2007 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE WESTERN NEBRASKA PANHANDLE AND SOUTHEAST WYOMING. .DAY ONE...TODAY AND TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT. && THIS PRODUCT...ALONG WITH OTHER WEATHER...HYDROLOGIC...AND CLIMATE INFORMATION IS AVAILABLE ON THE WEB AT... HTTP://WEATHER.GOV/CHEYENNE
1 high wind. Local standard time, as filed.
Microburst wind gusts around 60 mph from Cheyenne Airport to 2 miles southeast of Cheyenne.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2007Every state in 2007This day in weather historyWarnings in Wyoming, May 2007
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: 20702.