Increasing moisture, an upper level disturbance, and unusually hot temperatures created a very unstable environment that led to scattered afternoon and evening thunderstorms. Some of the storms produced strong winds and heavy rainfall.
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 TWC wrote it up.
Increasing moisture, an upper level disturbance, and unusually hot temperatures created a very unstable environment that led to scattered afternoon and evening thunderstorms. Some of the storms produced strong winds and heavy rainfall.
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 Tucson, AZ wrote its last area forecast discussion before the first event at Aug 31, 2:30 PM MST, 15 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TUCSON AZ 230 PM MST WED AUG 31 2011 .SYNOPSIS...MOISTURE INCREASE TODAY WILL LEAD TO GREATER CHANCE FOR MORE AREAS TO SEE THUNDERSTORMS THIS AFTERNOON AND EVENING. SCATTERED THUNDERSTORM ACTIVITY WILL REMAIN ACROSS SOUTHEAST ARIZONA INTO THE WEEKEND WITH TEMPERATURES NOT QUITE AS HOT. && .DISCUSSION...THUNDERSTORM ACTIVITY MUCH MORE WIDESPREAD WITH OVERALL GREATER AVAILABLE MOISTURE DESPITE SOME BOUNDARY LAYER DRYING. MID LEVEL SOUTHERLY FLOW FOR STEERING STORMS AND SEVERAL OUTFLOWS AT THE SURFACE IN THE OFFING TODAY. STRONG WINDS WILL BE AN ISSUE. 12Z UAZ RUCWRF SHOWED BIG DAY FOR SANTA CRUZ...EASTERN PIMA AND THE TOHONO OODHAM NATION...GOOD FOCUS ON BEST TONGUE OF MOISTURE IN BETWEEN DRIER AREAS WEST AND EAST. THIS CORRESPONDS TO H7 THETA-E MAXIMA AREA MODELS WERE ADVERTISING YESTERDAY AND SEEMS TO BE WORKING OUT WELL. ENOUGH MOISTURE AND GOOD ENOUGH FLOW ON THE WESTERN FLANK OF THE RIDGE TO KEEP SOUTHEAST ARIZONA IN SOME FLAVOR OF THUNDERSTORM ACTIVITY THROUGH THE WEEKEND. && .AVIATION...BKN CLOUDS AT 6-10K FT AGL TIL 06Z THURSDAY...THEN SLOWLY DECREASING CLOUDS THROUGH 12Z THURSDAY. SCATTERED TSRA/SHRA THROUGH 04Z THURSDAY...WITH TSRA/SHRA DIMINISHING BETWEEN 04Z-08Z THURSDAY. EXPECT BKN-OVC CEILINGS AT 4-6K FT AGL NEAR TSRA/SHRA...WITH MVFR CIGS/VSBYS NEAR THE STRONGER STORMS. SURFACE WIND GENERALLY LESS THAN 10 KTS...EXCEPT STRONG AND GUSTY NEAR THUNDERSTORMS. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS. && .FIRE WEATHER...SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED INTO THE UPCOMING WEEKEND. NORMAL DIURNAL WIND TRENDS ARE ALSO FORECASTED... EXCEPT FOR STRONG AND GUSTY WINDS NEAR THUNDERSTORMS. A GRADUAL LOWERING OF DAYTIME HIGH TEMPERATURES CAN BE EXPECTED THE NEXT COUPLE OF DAYS. && .CLIMATE...AUGUST AND METEOROLOGICAL SUMMER 2011 ARE HEADED FOR THE RECORD BOOKS AS ONE OF THE HOTTEST...IF NOT HOTTEST ON RECORD. AT THE CLOSE OF TODAY...TUCSON WILL END UP RECORDING ITS 2ND HOTTEST AUGUST AND METEOROLOGICAL SUMMER ON RECORD...WHILE DOUGLAS WILL RECORD ITS HOTTEST AUGUST AND SUMMER ON RECORD. SAFFORD IS ON COURSE TO RECORD EITHER ITS SECOND OR THIRD HOTTEST AUGUST AND 7TH HOTTEST SUMMER ON RECORD. FINAL NUMBERS WILL BE RELEASED ON THURSDAY. && .TWC WATCHES/WARNINGS/ADVISORIES...NONE. WEATHER.GOV/TUCSON
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE TUCSON AZ 154 PM MST WED AUG 31 2011 AZZ503>515-012100- UPPER SANTA CRUZ RIVER VALLEY/ALTAR VALLEY-TUCSON METRO AREA- SOUTH CENTRAL PINAL COUNTY-SOUTHEAST PINAL COUNTY- UPPER SAN PEDRO RIVER VALLEY- EASTERN COCHISE COUNTY BELOW 5000 FEET-UPPER GILA RIVER VALLEY- WHITE MOUNTAINS OF GRAHAM AND GREENLEE COUNTIES- GALIURO AND PINALENO MOUNTAINS-CHIRICAHUA MOUNTAINS- DRAGOON AND MULE AND HUACHUCA AND SANTA RITA MOUNTAINS- CATALINA AND RINCON MOUNTAINS-BABOQUIVARI MOUNTAINS- 154 PM MST WED AUG 31 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST ARIZONA. .DAY ONE...THIS AFTERNOON AND TONIGHT SCATTERED SHOWERS AND THUNDERSTORMS WILL MOVE OFF OF THE HIGHER TERRAIN AND INTO VALLEY LOCATIONS TODAY. SOME STORMS WILL GENERATE LOCALLY HEAVY RAINFALL AND STRONG GUSTY WINDS. PLEASE NOTE THAT EVEN MODERATE RAINFALL OVER THE RECENT BURN AREAS COULD RESULT IN FLASH FLOODING. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY THERE WILL BE SUFFICIENT MOISTURE FOR A CHANCE OF MAINLY AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS. PLEASE NOTE THAT EVEN MODERATE RAINFALL OVER THE RECENT BURN AREAS COULD RESULT IN FLASH FLOODING. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. AZZ501-502-012100- WESTERN PIMA COUNTY-TOHONO O'ODHAM NATION- 154 PM MST WED AUG 31 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST ARIZONA. .DAY ONE...THIS AFTERNOON AND TONIGHT ISOLATED SHOWERS AND THUNDERSTORMS ARE POSSIBLE LATER IN THE AFTERNOON AND EVENING HOURS...ESPECIALLY IN EASTERN AREAS. SOME STORMS MAY GENERATE STRONG GUSTY WINDS AND LOCALLY HEAVY RAINFALL. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY A CHANCE OF SHOWERS AND THUNDERSTORMS WILL CONTINUE. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. WEATHER.GOV/TUCSON
The Tucson radar (KEMX), 59 km away, was scanning. The volume nearest the first event began at 21:47 UTC.
1 thunderstorm wind. Local standard time, as filed.
Thunderstorms winds downed trees and power poles in Rio Rico along Interstate 19.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2011Every state in 2011This day in weather historyWarnings in Arizona, 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: 344019.