Abundant moisture remained in place. The monsoon high was nearly overhead which resulted in isolated but very slow moving thunderstorms that produced heavy rain and 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.
Abundant moisture remained in place. The monsoon high was nearly overhead which resulted in isolated but very slow moving thunderstorms that produced heavy rain and 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 Aug 20, 2:15 PM MST, 4 hours 5 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TUCSON AZ 215 PM MST MON AUG 20 2012 .SYNOPSIS...SCATTERED MAINLY AFTERNOON AND EVENING THUNDERSTORMS WILL CONTINUE THIS WEEK. THUNDERSTORM CHANCES WILL INCREASE MIDWEEK AS AN UPPER LEVEL DISTURBANCE MOVES ACROSS THE AREA. A DRYING TREND IS ON TAP THIS WEEKEND AS DEEPER MOISTURE MOVES EAST OF THE AREA. && .DISCUSSION...VARIOUS NWP MESOSCALE MODELS DEPICT THE FAVORED AREAS FOR SHOWERS/TSTMS INTO THIS EVENING TO OCCUR SOUTH AND WEST OF TUCSON...AND ACROSS THE HIGHER TERRAIN EAST OF TUCSON. MOISTURE IS SUFFICIENT TO JUSTIFY CHANCE-CATEGORY POPS MOST SECTIONS THRU THIS EVENING. THE BULK OF SHOWERS/TSTMS ARE EXPECTED TO END AROUND MIDNIGHT FOLLOWED BY DECREASING CLOUDINESS LATE TONIGHT. TUE-WED...MID-LEVEL STEERING FLOW TO REMAIN SELY/SLY TUE AS UPPER HIGH BECOMES CENTERED JUST EAST OF THE AREA. UPPER HIGH IS PROGGED TO BE OVER NRN CHIHUAHUA WED AS UPPER LOW APPROACHES THE SRN CALIFORNIA COAST. SCATTERED MAINLY AFTERNOON AND EVENING SHOWERS/ TSTMS TO OCCUR TUE-WED. PRECIP CHANCES TO BE ENHANCED SOMEWHAT WED VERSUS TUE AS UPPER DISTURBANCE MOVES NWD ACROSS THE AREA. THUR...20/12Z GFS/ECMWF WERE QUITE SIMILAR WITH DEPICTING UPPER HIGH TO BE SUPPRESSED SOUTH OF THE AREA AS SRN CALIFORNIA UPPER LOW TO MOVES EWD ACROSS NRN AZ. CHANCE-CATEGORY POPS TO CONTINUE MOST SECTIONS THUR. AT THIS TIME THERE APPEARS TO BE SOMEWHAT OF AN INCREASED RISK FOR SEVERE TSTMS MORE CHARACTERISTIC OF THE CENTRAL CONUS PLAINS ON THUR. FRI-MON...GRADUAL DRYING TREND IS PROGGED TO OCCUR THIS PERIOD. HAVE MAINTAINED ISOLATED-SCATTERED AFTERNOON AND EVENING SHOWERS/TSTMS FROM TUCSON EWD/SWD FRI-MON. PRECIP-FREE CONDITIONS ARE FORECAST ACROSS WRN PIMA COUNTY. COOLING TREND IS ON TAP WED-THUR FOLLOWED BY A WARMING TREND FRI-MON. && .AVIATION...SCT TSRA/SHRA INTO THIS EVENING THEN BULK OF PRECIP TO END AROUND 06Z TUESDAY. SCT TSRA/SHRA TO OCCUR TUESDAY AFTERNOON. OTHERWISE...VFR CONDITIONS AND SURFACE WIND LESS THAN 10 KTS THRU TUESDAY AFTERNOON OR 22/00Z. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS. && .FIRE WEATHER...EXPECT SCATTERED MAINLY AFTERNOON AND EVENING THUNDERSTORMS THIS WEEK. THE CHANCE OF THUNDERSTORMS WILL INCREASE MIDWEEK AS AN UPPER LEVEL DISTURBANCE MOVES ACROSS THE AREA. STRONG...ERRATIC AND GUSTY WINDS WILL OCCUR NEAR THUNDERSTORMS. OTHERWISE...EXPECT NORMAL DIURNAL WIND TRENDS THIS WEEK. && .TWC WATCHES/WARNINGS/ADVISORIES...NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE TUCSON AZ 915 AM MST MON AUG 20 2012 AZZ501>515-210600- 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- 915 AM MST MON AUG 20 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST ARIZONA. .DAY ONE...TODAY AND TONIGHT AMPLE MOISTURE REMAINS ACROSS SOUTHEAST ARIZONA FOR A GENERAL SCATTERED COVERAGE OF SHOWERS AND THUNDERSTORMS TODAY. WARMER AIR ALOFT WILL LIMIT THE OVERALL INTENSITY OF INDIVIDUAL STORMS FROM TUCSON EAST. EXPECT STORMS TO DEVELOP OVER THE HIGHER TERRAIN LATE THIS MORNING...AND STRUGGLE TO MOVE OFF THE MOUNTAINS INTO THE VALLEYS THIS AFTERNOON. ALTHOUGH THESE STORMS WILL STILL BE ABLE TO PRODUCE LOCALLY HEAVY RAINFALL AND STRONG GUSTY WINDS...THE RISK OF WIDESPREAD FLOODING ISSUES OR DAMAGING DOWNBURST WINDS IS RELATIVELY LOW. THE MORE FAVORED AREAS FOR THUNDERSTORMS WILL BE TO THE SOUTH AND SOUTHWEST OF TUCSON...ESPECIALLY OVER SANTA CRUZ...CENTRAL AND WESTERN PIMA COUNTIES INCLUDING THE TOHONO OODHAM NATION. STORMS IN THIS AREA WILL BE FREE FROM THE WARM AIR ALOFT AND HAVE THE CAPABILITY OF BECOMING MORE ORGANIZED AS THEY TRACK TO THE WEST AT 10 TO 15 MPH. THE MOIST ATMOSPHERE IN PLACE WILL RESULT IN A MODERATE RISK OF LOCALIZED FLOODING ISSUES AND DAMAGING DOWNBURST WINDS. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY AN INCREASE IN SHOWER AND THUNDERSTORM ACTIVITY IS EXPECTED MIDWEEK AS A DISTURBANCE MAKES IT WAY NORTH INTO SOUTHEAST ARIZONA. THIS WILL BE FOLLOWED BY A STRONG DECREASE IN THUNDERSTORM ACTIVITY FRIDAY...PERSISTING INTO THE WEEKEND. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. WEATHER.GOV/TUCSON
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TUCSON AZ
335 PM MST MON AUG 20 2012
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0738 PM TSTM WND DMG TUCSON 32.24N 110.94W
08/19/2012 PIMA AZ NWS EMPLOYEE
HOUGHTON AND DREXEL 4-6 TREE BRANCH DOWN
&&
EVENT NUMBER TWC1200073
JMThe Tucson radar (KEMX), 112 km away, was scanning. The volume nearest the first event began at 01:19 UTC.
1 flash flood. Local standard time, as filed.
Heavy rain caused most washes that cross Indian Road 19 to flow rapidly. Motorists were rescued from their vehicle near South Komelik.
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, August 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: 409034.