Abundant moisture and favorable flow allowed for thunderstorms that produced 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.
Abundant moisture and favorable flow allowed for thunderstorms that produced 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 20, 9:20 AM MST, 3 hours 10 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TUCSON AZ 920 AM MST SAT AUG 20 2011 .SYNOPSIS...EXPECT SCATTERED SHOWERS AND THUNDERSTORMS OVER THE WEEKEND INTO NEXT WEEK...WITH HOTTER TEMPERATURES DURING THE NEW WEEK. && .DISCUSSION...NO REAL CHANGES IN PREVIOUS THOUGHTS ON THUNDERSTORM CHANCES TODAY. THE TUCSON 12Z UPPER-AIR SOUNDING SHOWED A WEAK STEERING FLOW IN PLACE TODAY WITH SOME PROMISING INSTABILITY FOR THIS AFTERNOON. THAT SAID...THE MAIN FORECAST UNCERTAINTY WILL BE WHETHER OR NOT ISOLATED STORMS THAT DEVELOP IN THE MOUNTAINS CAN PROPAGATE INTO THE VALLEYS GIVEN THE WEAK MID-LEVEL FLOW IN PLACE. SINCE THE BOUNDARY LAYER HAS RECOVERED FROM THE ACTIVE THUNDERSTORM DAY ON THURSDAY WHICH LEAD TO VERY LITTLE ACTIVITY YESTERDAY...WILL EXPECT BETTER THUNDERSTORM COVERAGE TODAY. AS USUAL...MAIN THREAT FROM THUNDERSTORMS THIS AFTERNOON AND EVENING WILL BE STRONG WINDS AND LOCALLY HEAVY DOWNPOURS. && .AVIATION...MOSTLY CLEAR THIS MORNING...ISOLD-SCT TSRA/SHRA TO OCCUR 18Z TODAY TO 03Z SUNDAY. OTHERWISE...FEW-BKN CLOUDS WITH BASES AT 6-10K FT AGL AND SURFACE WIND MAINLY LESS THAN 10 KTS THRU SUNDAY MORNING OUTSIDE OF ANY STRONG GUSTY THUNDERSTORM WINDS. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS. && .FIRE WEATHER...EXPECT ISOLATED TO SCATTERED THUNDERSTORMS INTO NEXT WEEK. NORMAL DIURNAL WIND TRENDS WILL OCCUR...EXCEPT STRONG AND GUSTY WINDS WILL PREVAIL NEAR THUNDERSTORMS. && .PREV DISCUSSION...AS THE RIDGE RETROGRADES OVERHEAD EARLY IN THE NEW WEEK...TEMPERATURES WILL CLIMB ACROSS THE AREA. HEAT IS GOOD...BUT NOT IN THE MID LEVELS AND ANY SUBSEQUENT SUBSIDENCE INVERSION MAY SLOW STORM DEVELOPMENT DOWN A BIT. MEDIUM RANGE MODELS RECONSOLIDATE THE HIGH CENTER FURTHER NORTH BY THE END OF NEXT WEEK FOR ANOTHER POTENTIAL UPSWING IN ACTIVITY. TYPICAL LATE AUGUST COMINGS AND GOINGS. && .TWC WATCHES/WARNINGS/ADVISORIES...NONE. WEATHER.GOV/TUCSON
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE TUCSON AZ 938 AM MST SAT AUG 20 2011 AZZ503-507>515-210645- UPPER SANTA CRUZ RIVER VALLEY/ALTAR VALLEY- 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- 938 AM MST SAT AUG 20 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST ARIZONA. .DAY ONE...TODAY AND TONIGHT ISOLATED SHOWERS AND THUNDERSTORMS WILL DEVELOP IN THE MOUNTAINS BY NOON TODAY. SHOWERS AND THUNDERSTORMS WILL BECOME MORE SCATTERED ACROSS THE AREA THIS AFTERNOON AND EVENING. THE MAIN CONCERNS FROM THE STRONGER THUNDERSTORMS WILL BE DAMAGING WINDS AND LOCALLY HEAVY DOWNPOURS THAT COULD RESULT IN RUNOFF PROBLEMS LIKE FLOODED ROADS AND NORMALLY DRY WASHES. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY THE CHANCE OF DAILY THUNDERSTORMS WILL CONTINUE THROUGH THE WEEK. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. AZZ502-504>506-210645- TOHONO O'ODHAM NATION-TUCSON METRO AREA- SOUTH CENTRAL PINAL COUNTY-SOUTHEAST PINAL COUNTY- 938 AM MST SAT AUG 20 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST ARIZONA. .DAY ONE...TODAY AND TONIGHT THE SHOWERS AND THUNDERSTORMS THAT MANAGED TO DEVELOP TODAY WILL BE ISOLATED IN NATURE AND EXHIBIT SLOW AND ERRATIC MOVEMENT. THE MAIN CONCERNS FROM SOME OF THE STRONGER THUNDERSTORMS WILL BE LOCALLY HEAVY DOWNPOURS AND STRONG WIND. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY THE CHANCE OF DAILY THUNDERSTORMS WILL CONTINUE THROUGH THE WEEK. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. AZZ501-210645- WESTERN PIMA COUNTY- 938 AM MST SAT AUG 20 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST ARIZONA. .DAY ONE...TODAY AND TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. WEATHER.GOV/TUCSON
The Tucson radar (KEMX), 62 km away, was scanning. The volume nearest the first event began at 19:29 UTC.
2 flash flood. Local standard time, as filed.
Heavy rainfall over the Monument Fire burn area resulted in flooding in Miller Canyon and the closure of Miller Canyon Road.
Heavy rainfall lead to a quick five foot rise in the Nogales Wash and subsequent flooding along its banks.
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: 343929, 343930.