5 inches of precipitable water to produce thunderstorms with heavy rain over southern Arizona. Some of the heavy rain resulted in flash flooding.
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.
A weak upper level low in weak southwest flow aloft acted on over 1.5 inches of precipitable water to produce thunderstorms with heavy rain over southern Arizona. Some of the heavy rain resulted in flash flooding.
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 Sep 10, 1:57 PM MST, 1 hour 18 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TUCSON AZ 157 PM MST MON SEP 10 2012 .SYNOPSIS...A WEAK WEATHER SYSTEM WILL PASS THROUGH THE REGION BRINGING MORE WIDESPREAD SHOWERS AND THUNDERSTORMS TO THE AREA TONIGHT AND TUESDAY. A DRIER WESTERLY FLOW WILL LEAD TO MUCH LESS THUNDERSTORM ACTIVITY AFTER WEDNESDAY. && .DISCUSSION...THE UPPER LOW WAS STILL SPINNING OVER NORTHERN BAJA THIS AFTERNOON...BUT WAS STARTING TO SHOW SIGNS OF LIFTING NORTHWARD. AN IMPULSE EMBEDDED IN THE SOUTHERLY FLOW ALOFT AHEAD OF THE LOW CENTER WAS TRIGGERING THUNDERSTORMS IN SANTA CRUZ COUNTY INTO SONORA MEXICO ALREADY THIS AFTERNOON. THAT SAID...EXPECTING A RATHER ACTIVE AFTERNOON AND EVENING FOR THUNDERSTORMS ACROSS SOUTHEAST ARIZONA...ESPECIALLY ACROSS PIMA...PINAL AND SANTA CRUZ COUNTIES. LOOKING AT STORMS TRACKING NORTH WITH MULTIPLE CELLS PASSING THROUGH THE SAME GENERAL AREA THIS AFTERNOON AND EARLY THIS EVENING. SO FLOODING AND FLASH FLOODING WILL BE THE MAIN THREATS FROM THUNDERSTORMS. LATEST MODELS CONTINUED TO TRACK THE BAJA LOW NORTHWARD AND WEAKEN AS IT PASSES THROUGH NORTHERN ARIZONA. THE COMBINATION OF DEEP MOISTURE IN PLACE AND DYNAMICS FROM THE LOW WILL RESULT IN WIDESPREAD SHOWERS AND THUNDERSTORMS TONIGHT THROUGH LATE TUESDAY. LOCALLY HEAVY RAINFALL WILL BE THE MAIN THREAT. THEREAFTER...A DRY WESTERLY FLOW ALOFT WAS PROGGED TO DEVELOP OVER THE REGION. THIS WILL RESULT IN DIMINISHING RAIN CHANCES WEDNESDAY AND MORE SO THURSDAY. OVER THE WEEKEND...A RIDGE OF HIGH PRESSURE WAS PROGGED TO BUILD OVER THE DESERT SOUTHWEST FOR HOTTER AFTERNOON TEMPERATURES. && .HYDROLOGY...THE VAMORI WASH NEAR KOM VO IN CENTRAL PIMA COUNTY REMAINED ABOVE BANKFULL. A FLOOD WARNING FOR THIS AREA WILL CONTINUE THROUGH THIS EVENING. ADDITIONAL RAINFALL AND SUBSEQUENT RUNOFF WILL LIKELY KEEP WATER LEVELS UP THROUGH TONIGHT. OTHER SMALL STREAMS AND WASHES WERE EXPERIENCING ELEVATED FLOWS ACROSS THE TOHONO O'ODHAM NATION TODAY. && .AVIATION...MAINLY SCT-BKN CLOUDS 6-10K FT AGL WILL CONTINUE INTO TUESDAY MORNING. THE BEST CHANCE OF -SHRA/-TSRA WILL CONTINUE TO BE FROM KTUS WESTWARD WITH MORE ISOLATED COVERAGE EAST OF KTUS. GUSTY WINDS TO 40 KTS AND MVFR CONDITIONS POSSIBLE WITH -TSRA. OTHERWISE...GENERALLY LIGHT WINDS AND VFR CONDITIONS WILL PREVAIL INTO TUESDAY MORNING. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS. && .FIRE WEATHER...SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH LATE TUESDAY. BY WEDNESDAY...DRIER WESTERLY FLOW ALOFT WILL BEGIN TO MOVE IN RESULTING IN A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS EAST OF TUCSON INTO THIS WEEKEND. && .TWC WATCHES/WARNINGS/ADVISORIES...NONE. && VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/TUCSON
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE TUCSON AZ 857 AM MST MON SEP 10 2012 AZZ501>515-110600- WESTERN PIMA COUNTY-TOHONO O'ODHAM NATION- 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- 857 AM MST MON SEP 10 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST ARIZONA. .DAY ONE...TODAY AND TONIGHT SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED ONCE AGAIN TODAY FOR SOUTHEAST ARIZONA...WITH THE GREATEST COVERAGE FROM THE TUCSON AREA WESTWARD. WITH ABUNDANT MOISTURE IN THE ATMOSPHERE...THE PRIMARY CONCERN WILL CONTINUE TO BE HEAVY RAINFALL. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY AN AREA OF LOW PRESSURE WILL MOVE ACROSS ARIZONA TUESDAY RESULTING IN CONTINUED SCATTERED SHOWERS AND THUNDERSTORMS WITH MORE HEAVY RAINFALL POSSIBLE. THEREAFTER...DRIER AIR WILL START TO MOVE IN FROM THE WEST WHICH WILL RESULT IN A DOWNWARD TREND IN STORMS. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. WEATHER.GOV/TUCSON
The Tucson radar (KEMX), 49 km away, was scanning. The volume nearest the first event began at 22:14 UTC.
1 flash flood. Local standard time, as filed.
Heavy rain caused flash flooding on the southwest side of Tucson. A small wash that crosses Valencia Road overflowed, causing closure of the road between Viviana and Camino Verde. Several yards in the area were also flooded.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2012Every state in 2012This day in weather historyWarnings in Arizona, September 2012
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: 414348.