Favorable positioning of the monsoon high pressure system across New Mexico allowed for increasing moisture across southern Arizona. A weak low pressure system off the Baja Peninsula also helped to initiate scattered showers and thunderstorms across southern Arizona.
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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.
Favorable positioning of the monsoon high pressure system across New Mexico allowed for increasing moisture across southern Arizona. A weak low pressure system off the Baja Peninsula also helped to initiate scattered showers and thunderstorms across southern Arizona. Some of the storms 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 13, 1:20 PM MST, 4 hours 41 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TUCSON AZ 120 PM MST SAT AUG 13 2011 .SYNOPSIS...ISOLATED TO SCATTERED MAINLY AFTERNOON AND EVENING THUNDERSTORMS WILL CONTINUE INTO NEXT WEEK. && .DISCUSSION...12Z UPPER AIR PLOTS PLACED 300 MB HIGH CENTER JUST EAST OF THE TEXAS BIG BEND WHILE THE 500 AND 700 MB HIGH WAS OVER NE NEW MEXICO. 12Z TUCSON/EL PASO SOUNDINGS SHOWED LITTLE STEERING FLOW WHILE IT WAS MUCH STRONGER ON THE 12Z PHOENIX SOUNDING. PRECIPITABLE WATER VALUES REMAIN RATHER HIGH ACROSS THE AREA WITH VALUES...BASED ON VARIOUS SOURCES...RANGING FROM 1.25" EAST TO 1.80" WEST. WATER VAPOR IMAGERY SHOWED A WEAK UPPER LOW OFF NORTHERN BAJA...REMAINS OF MORNING MCS OVER NORTHERN SINALOA MEXICO MOVING NNW...A POSSIBLE WEAK DISTURBANCE ALOFT OVER CHIHUAHUA MEXICO...WHERE ISOLATED TO SCATTERED THUNDERSTORMS WERE OCCURRING. ACROSS SOUTHEAST ARIZONA...AS OF 1 PM...DEEPER CONVECTION HAS BEEN STRUGGLING...WITH BETTER STORMS OVER THE NM BOOT AND WESTERN CHIHUAHUA MEXICO. WHAT HAPPENING IN CHIHUAHUA GIVES ME BETTER CONFIDENCE THAT THE 12Z NAM HAS THE RIGHT IDEA OF POTENTIAL BIG MCS DEVELOPING SOUTH OF COCHISE COUNTY LATER TODAY. HAVE UPPED POPS ACROSS SOUTHERN HALF OF COCHISE COUNTY AND SANTA CRUZ COUNTY FOR TONIGHT. HEAVY RAIN MAIN THREAT WITH THESE STORMS...ALTHOUGH CANT RULE OUT A WET MICROBURST OR TWO. SUN...IF 12Z NAM IS CORRECT...THERE WILL BE A LOT OF DEBRIS CLOUDS AROUND IN THE MORNING...ESPECIALLY FROM TUCSON EAST...ALONG WITH A POSSIBLE MCV SOUTH OF COCHISE COUNTY WHICH COULD DRIFT TO THE N AND IMPACT THE THUNDERSTORM COVERAGE ALONG THE INTERNATIONAL BORDER BETWEEN NOGALES AND DOUGLAS DURING THE AFTERNOON HOURS. HIGHS WILL BE RIGHT AROUND NORMAL. MON...LOW END MONSOON FORECAST AS DRIER AIR PUSHES IN FROM THE WEST. HIGHS WILL BE RIGHT AROUND NORMAL. TUE-THU...WILL CONTINUE TO SEE A DRY INFLUX OF AIR FROM THE WEST. HOWEVER WE WILL HANG ON TO ENOUGH MOISTURE TO KEEP SLIGHT CHANCE/LOW END CHANCE VALUES IN THE FORECAST. HIGHS WILL BE SEVERAL DEGREES WARMER THAN NORMAL. FRI-SAT...MODELS INDICATING POSSIBLE BETTER MID-LEVEL FLOW WHICH COULD LEAD TO AN UPTICK IN AREAL COVERAGE OF STORMS. && .AVIATION...ISOLD-SCT TSRA/SHRA CONTINUING THRU 03Z SUNDAY WITH PRECIP DECREASING IN COVERAGE BETWEEN 03Z-06Z SUNDAY. ISOLD-SCT TSRA/SHRA DVLPG AGAIN BETWEEN 18Z-23Z SUNDAY. MVFR CIGS/VSBYS AND WIND GUSTS TO 45 KTS WITH THE STRONGER TSRA. OTHERWISE...SCT-BKN CLOUDS WITH BASES AT 6-8K FT AGL AND BKN-OVC CLOUDS AT 12-15K FT AGL BETWEEN 22Z-04Z SUNDAY. SURFACE WIND GENERALLY LESS THAN 10 KTS... EXCEPT STRONG AND GUSTY NEAR THUNDERSTORMS. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS. && .FIRE WEATHER...ISOLATED TO SCATTERED MAINLY AFTERNOON AND EARLY EVENING SHOWERS AND THUNDERSTORMS THROUGH THE MIDDLE OF THE UPCOMING WEEK. THE BEST CHANCE FOR MEASURABLE PRECIPITATION WILL BE IN THE HIGHER TERRAIN SOUTH AND EAST OF TUCSON. OTHERWISE...NORMAL DIURNAL WIND TRENDS ARE EXPECTED...EXCEPT FOR STRONG AND GUSTY WINDS NEAR THUNDERSTORMS. && .TWC WATCHES/WARNINGS/ADVISORIES...NONE. WEATHER.GOV/TUCSON
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE TUCSON AZ 1225 PM MST SAT AUG 13 2011 AZZ503-507>515-140600- 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- 1225 PM MST SAT AUG 13 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST ARIZONA. .DAY ONE...TODAY AND TONIGHT SCATTERED THUNDERSTORMS ARE EXPECTED THROUGH TONIGHT. THE MAIN THREAT WILL BE LOCALLY HEAVY RAINFALL DUE TO VERY SLOW MOVEMENT OF THUNDERSTORMS. ALSO...WIND GUSTS OF 40 TO 50 MPH MAY OCCUR WITH THE STRONGER THUNDERSTORMS. PLEASE NOTE THAT EVEN MODERATE RAINFALL OVER THE RECENT BURN AREAS COULD RESULT IN FLASH FLOODING. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY THERE WILL BE A CHANCE OF THUNDERSTORMS EACH DAY. THE MAIN THREATS WILL BE LOCALLY HEAVY RAIN AND GUSTY WINDS. ALSO...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. AZZ502-504>506-140600- TOHONO O'ODHAM NATION-TUCSON METRO AREA- SOUTH CENTRAL PINAL COUNTY-SOUTHEAST PINAL COUNTY- 1225 PM MST SAT AUG 13 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST ARIZONA. .DAY ONE...TODAY AND TONIGHT ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED LATER THIS AFTERNOON THROUGH TONIGHT. THE MAIN THREAT WILL BE LOCALLY HEAVY RAINFALL DUE TO VERY SLOW MOVEMENT OF THUNDERSTORMS. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY THERE WILL BE A SLIGHT CHANCE OF MAINLY AFTERNOON AND EVENING THUNDERSTORMS EACH DAY. THE MAIN THREATS WILL BE LOCALLY HEAVY RAIN AS WELL AS GUST WINDS OVER 50 MPH. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. AZZ501-140600- WESTERN PIMA COUNTY- 1225 PM MST SAT AUG 13 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST ARIZONA. .DAY ONE...TODAY AND TONIGHT ISOLATED THUNDERSTORMS ARE POSSIBLE THROUGH TONIGHT. THE MAIN THREAT WILL BE LOCALLY HEAVY RAINFALL DUE TO VERY SLOW MOVEMENT OF THUNDERSTORMS. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY THERE WILL BE A SLIGHT CHANCE OF MAINLY LATE AFTERNOON AND EVENING THUNDERSTORMS EACH DAY. THE MAIN THREATS WILL BE GUSTY WINDS OVER 50 MPH AND LOCALLY HEAVY RAIN. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. WEATHER.GOV/TUCSON
The Tucson radar (KEMX), 55 km away, was scanning. The volume nearest the first event began at 01:02 UTC.
1 flash flood. Local standard time, as filed.
Rainfall in excess of one inch under one hour on the Monument Fire burn area resulted in flooding along Montezuma Canyon Road. Heavy rainfall also resulted in water rushing across and down Hereford Road making the road impassable.
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: 340263.