Strong winds downed power lines and caused scattered outages.
Every event with a place to put it. 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 BOU wrote it up.
Strong winds downed power lines and caused scattered outages.
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 Denver/Boulder, CO wrote its last area forecast discussion before the first event at Aug 8, 3:11 PM MST, 2 hours 14 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DENVER/BOULDER CO 411 PM MDT MON AUG 8 2011 .UPDATE... && .SHORT TERM...SOME CONCERN ABOUT SEVERE THUNDERSTORM POTENTIAL FOR THE FAR NORTHEAST PLAINS OF COLORADO...SO HAVE OPTED TO GO WITH A SEVERE THUNDERSTORM WATCH FOR ZONES 48>51 UNTIL MIDNIGHT MDT TONIGHT. STG WINDS TO 60 MPH AND HAIL TO ONE INCH THE MAIN THREATS. .PREV DISCUSSION... /ISSUED 240 PM MDT MON AUG 8 2011/ SHORT TERM...FRONTAL BOUNDARY ASSOCIATED WITH SURFACE HIGH PRESSURE IS BUILDING IN FROM NORTHEAST THIS AFTERNOON. OVERALL IT STILL APPEARS TOO DRY AND STABLE FOR THUNDERSTORMS ALONG THE FRONT RANGE THIS EVENING. MAIN POTENTIAL WL BE OVER THE FAR NORTHEASTERN PLAINS WHERE FCST CAPES IN THE 1000-1500 J/KG RANGE ARE STILL PROGGED. A 90 KT UPPER JET MOVING ACROSS SRN WY/NRN CO MAY HELP INITIATE DEEP CONVECTION AS WELL...BUT IT SHOULD MOVE QUICKLY TO THE EAST. 17Z HRRR MDL SHOWS ALL OF THE DEEP CONVECTION DEVELOPING THERE THIS EVENING AS WELL WITH THE BEST POTENTIAL OVER NEBRASKA. WL MAINTAIN 10-20 PERCENT POPS FOR ZONES 48>51 THROUGH 06Z THIS EVENING. OVERNIGHT...NAM12 INDICATE BOUNDARY LYR MOISTURE INCREASING AS WEAK DENVER CYCLONE FORMS. HIGHER DEWPOINTS ARE PROGGED TO ADVECT INTO FRONT RANGE NORTH OF DENVER. WL ADD PATCHY FOG TO THE GRIDS 09-15Z PRIMARILY NORTH AND EAST OF DENVER. STRONG WEST TO NORTHWESTERLY FLOW ALOFT WILL CONTINUE OVER COLORADO IN THE AFTN WITH 300 MB WINDS STILL 65-70 KTS. FCST CAPES ARE PROGGED TO RANGE FROM 400-1000 J/KG ALONG THE PALMER DIVIDE/FRONT RANGE. IT WILL BE SIGNIFICANTLY HIGHER OVER THE NORTHEAST PLAINS AROUND 2500 J/KG. SOME WEAK QG ASCENT AOA 700 MB AS WELL IN THE AFTN. WL CONTINUE WITH 30 PERCENT COVERAGE OVER ZONES 48>51...WITH LESSER COVERAGE OF 10-20 PERCENT COVERAGE FURTHER WEST AND SOUTH. LONG TERM...HIGH PRESSURE RIDGE ALOFT WILL REMAIN ACROSS MUCH OF THE SOUTHERN PORTIONS OF THE UNITED STATES FOR THE REST OF THE WEEK. THIS WILL LEAVE THE ROCKY MOUNTAIN REGION...INCLUDING COLORADO IN A BRISK WEST TO NORTHWEST FLOW PATTERN. THE RESULT WILL BE SEVERAL COLD FRONTS MOVING THROUGH NORTHEAST COLORADO...THE STRONGEST ON TUESDAY NIGHT WITH LOW LEVEL COOLING EXPECTED ON WEDNESDAY. TEMPERATURES WILL BE QUITE A BIT COOLER ESPECIALLY OVER THE FAR NORTHEAST PLAINS. THERE IS SOME DISAGREEMENT AMONGST THE MODELS ON THE MAGNITUDE OF THE COOLING WITH THE NAM THE COLDEST WITH STRONG LOW LEVEL STABILITY AND GFS THE WARMEST FOR DAYTIME ON WEDNESDAY. THE BEST CHANCE OF STORMS WILL ALSO BE TUESDAY NIGHT OVER THE FAR PLAINS WITH AN UPPER LEVEL DISTURBANCE PASSING BY. WITH THE STRONGER LOW LEVEL STABILITY AND STRATUS ACROSS THE PLAINS ON WEDNESDAY...CHANCES OF ANY STORMS LOOK QUITE LOW AND HAVE LOWERED POPS SOME MORE. WARMER AGAIN ON THURSDAY BEFORE NEXT WAVE AND ASSOCIATED COLD FRONT SEEPS INTO THE REGION EARLY ON FRIDAY. LOOKS LIKE ENOUGH MOISTURE WILL RETURN FOR SOME ISOLATED STORMS IN THE MOUNTAINS BY THIS WEEKEND. OVERALL ONLY MINIMAL CHANGES TO LONG TERM GRIDS. && .AVIATION...VFR CONDITIONS EXPECTED THROUGH TONIGHT. THE MDLS DO DEVELOP A WEAK DENVER CYCLONE OVERNIGHT...WITH INCREASING LOW LEVEL MOISTURE DEVELOPING TOWARDS 12Z. WL KEEP THE MENTION OF LOW CLOUDS AND FOG NORTH AND EAST OF DENVER INTERNATIONAL AIRPORT. NORTHEAST WINDS THIS AFTN WILL TRANSITION TO SELY THIS EVENING...THEN SWLY AFTER 06Z. .HYDROLOGY..NO THREAT OF FLOODING THROUGH TONIGHT. && .BOU WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...COOPER LONG TERM....ENTREKIN
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DENVER CO 1048 AM MDT MON AUG 08 2011 COZ030>051-091200- JACKSON COUNTY BELOW 9000 FEET-WEST JACKSON AND WEST GRAND COUNTIES ABOVE 9000 FEET-GRAND AND SUMMIT COUNTIES BELOW 9000 FEET-SOUTH AND EAST JACKSON/LARIMER/NORTH AND NORTHEAST GRAND/ NORTHWEST BOULDER COUNTIES ABOVE 9000 FEET-SOUTH AND SOUTHEAST GRAND/WEST CENTRAL AND SOUTHWEST BOULDER/GILPIN/CLEAR CREEK/ SUMMIT/NORTH AND WEST PARK COUNTIES ABOVE 9000 FEET-LARIMER AND BOULDER COUNTIES BETWEEN 6000 AND 9000 FEET-JEFFERSON AND WEST DOUGLAS COUNTIES ABOVE 6000 FEET/GILPIN/CLEAR CREEK/NORTHEAST PARK COUNTIES BELOW 9000 FEET-CENTRAL AND SOUTHEAST PARK COUNTY-LARIMER COUNTY BELOW 6000 FEET/NORTHWEST WELD COUNTY-BOULDER AND JEFFERSON COUNTIES BELOW 6000 FEET/WEST BROOMFIELD COUNTY-NORTH DOUGLAS COUNTY BELOW 6000 FEET/DENVER/WEST ADAMS AND ARAPAHOE COUNTIES/ EAST BROOMFIELD COUNTY-ELBERT/CENTRAL AND EAST DOUGLAS COUNTIES ABOVE 6000 FEET-NORTHEAST WELD COUNTY-CENTRAL AND SOUTH WELD COUNTY-MORGAN COUNTY-CENTRAL AND EAST ADAMS AND ARAPAHOE COUNTIES- NORTH AND NORTHEAST ELBERT COUNTY BELOW 6000 FEET/NORTH LINCOLN COUNTY-SOUTHEAST ELBERT COUNTY BELOW 6000 FEET/SOUTH LINCOLN COUNTY-LOGAN COUNTY-WASHINGTON COUNTY-SEDGWICK COUNTY-PHILLIPS COUNTY- 1048 AM MDT MON AUG 08 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST AND NORTH CENTRAL COLORADO. .DAY ONE...TODAY AND TONIGHT THERE IS A SLIGHT CHANCE OF THUNDERSTORMS THIS AFTERNOON AND EVENING OVER THE NORTHEAST CORNER OF COLORADO...EAST OF A LINE FROM BRIGGSDALE TO LAST CHANCE. THE THREAT OF SEVERE THUNDERSTORMS IS LOW. OTHERWISE IT WILL BE SUNNY AND SLIGHTLY COOLER THAN YESTERDAY AS HIGH PRESSURE ALOFT BUILDS OVER THE SOUTHWESTERN UNITED STATES. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY THERE WILL BE A SLIGHT CHANCE OF LATE DAY SHOWERS AND THUNDERSTORMS OVER THE PLAINS AND FOOTHILLS FROM TUESDAY THROUGH FRIDAY...THEN OVER ALL THE FORECAST AREA SATURDAY AND SUNDAY. TEMPERATURES WILL HOVER AROUND SEASONAL NORMALS FOR NEXT WEEK. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT. COOPER/ENTREKIN
The Cheyenne radar (KCYS), 152 km away, was scanning. The volume nearest the first event began at 00:25 UTC.
1 thunderstorm wind. Local standard time, as filed.
Strong thunderstorm winds snapped large tree branches, some up to 5 inches in diameter.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2011Every state in 2011This day in weather historyWarnings in Colorado, August 2011
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: 339534.