There was still enough moisture in the atmosphere to support scattered, heavy rain producing thunderstorms. The upper level high was centered off of the southern California coast, and was helping to push drier air into the area.
Every event with a place to put it; 2 filed by county or forecast zone are drawn at its center, in a lighter ring. 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.
There was still enough moisture in the atmosphere to support scattered, heavy rain producing thunderstorms. The upper level high was centered off of the southern California coast, and was helping to push drier air into the area. The convective activity was centered from Central Pima County, to Eastern Pima County out toward Santa Cruz County and out over the Mexican border.
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 Jul 28, 2:10 PM MST, 3 hours 20 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TUCSON AZ 210 PM MST WED JUL 28 2004 SOUTHEAST ARIZONA FORECAST DISCUSSION .SYNOPSIS...ENOUGH MOISTURE HANGING ON FOR ANOTHER AFTERNOON AND EVENING OF ISOLATED TO SCATTERED THUNDERSTORMS ACROSS SOUTHEAST ARIZONA. DRY NORTHWESTERLY FLOW ALOFT AROUND A WEST COAST RIDGE WILL LEAD TO A DECREASE IN THUNDERSTORMS THE SECOND HALF OF THE WEEK. THE UPPER HIGH WILL SHIFT EAST TO A MORE FAVORABLE POSITION EARLY IN THE NEW WEEK...WITH MOISTURE INCREASING AGAIN ACROSS THE AREA FOR MORE THUNDERSTORMS. && .DISCUSSION...CONVECTION LIMITED IN WESTERN AREAS THIS AFTERNOON WITH ISOLATED TO SCATTERED COVERAGE FROM ABOUT TUCSON EASTWARD AS DRIER AIR TRIES TO PUSH IN FROM THE WEST. THE 12Z YUMA SOUNDING WAS DOWN TO AROUND 1/2 OF AN INCH OF PRECIPITABLE WATER...WITH GOES SOUNDER ESTIMATES AND WATER VAPOR IMAGERY SHOWING THIS TREND SPREADING EASTWARD TODAY. GENERALLY ISOLATED COVERAGE SHOULD BE THE MOST WE CAN EXPECT THIS AFTERNOON AND EVENING...MAINLY EAST OF TUCSON...BUT WITH THE DRY AIR TRYING TO PUSH IN WE COULD SEE SOME HAIL AND MICROBURSTS. DRY FLOW AROUND THE HIGH CENTER TO OUR WEST WILL CONTINUE ANOTHER 36 TO 48 HOURS BEFORE THE RIDGE AXIS SHIFTS OVERHEAD. ON THE DRY SIDE FOR LATE JULY WITH TEMPERATURES BACK NEAR OR ABOVE 100 MANY PLACES. RIDGE AXIS TO OUR EAST SUNDAY AND MONDAY FOR A RETURN OF MOIST SOUTHEAST FLOW. MODELS HINTING AT THIS BUT STILL PROBABLY UNDERDONE. && .TWC WATCHES/WARNINGS/ADVISORIES...NONE. MEYER
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE TUCSON AZ 1115 AM MST WED JUL 28 2004 AZZ019-029>035-280700- NORTHERN GREENLEE COUNTY-UPPER GILA RIVER VALLEY-COCHISE COUNTY-SOUTHEAST PINAL COUNTY-TUCSON METRO/MARANA/GREEN VALLEY-SANTA CRUZ COUNTY-TOHONO OODHAM NATION-WESTERN PIMA COUNTY- 1115 AM MST WED JUL 28 2004 THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST ARIZONA .DAY ONE...TODAY SYNOPSIS...THE POTENTIAL FOR HEAVY RAINFALL AND STRONG DOWNBURST WINDS IS BELOW NORMAL ACROSS ALL OF SOUTHEAST ARIZONA TODAY. DAYTIME HEATING IN COMBINATION WITH MOISTURE IN PLACE WILL BRING ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS TO MUCH OF SOUTHEAST ARIZONA THIS AFTERNOON AND EVENING. ISOLATED ACTIVITY IS EXPECTED FROM SANTA CRUZ COUNTY...NORTH THROUGH THE EASTERN HALF PIMA COUNTY AND INTO SOUTHEAST PINAL COUNTY. SCATTERED CONVECTION IS EXPECTED ACROSS FAR EASTERN PORTIONS OF THE FORECAST AREA...ALONG THE NEW MEXICO BORDER. NO ACTIVITY IS FORECASTED ACROSS FAR WESTERN PIMA COUNTY TODAY. THE BEST CHANCES FOR DEVELOPMENT WILL BE IN THE WHITE MOUNTAINS AND POINTS SOUTH ALONG THE NEW MEXICO BORDER INTO COCHISE COUNTY. DISCUSSION...THE UPPER HIGH IS CURRENTLY CENTERED OFF OF THE SOUTHERN CALIFORNIA AND BAJA COASTS. WITH THE HIGH IN THIS POSITION AND NORTHWEST FLOW OVER THE RIDGE AXIS...DRIER AIR CONTINUES TO PUSH ACROSS SOUTHEAST ARIZONA. EXPECT THIS TREND TO CONTINUE TODAY WITH THE DRIER AIR TRYING TO PUSH INTO EASTERN PORTIONS OF THE FORECAST AREA BY TONIGHT. HOWEVER...THERE IS STILL ENOUGH MOISTURE IN PLACE OVER THE EASTERN HALF OF SOUTHEAST ARIZONA FOR ISOLATED TO SCATTERED AFTERNOON AND EVENING THUNDERSTORMS. THE BEST CHANCE FOR CONVECTION TODAY WILL BE SOUTH AND EAST OF A LINE FROM HANNAGAN MEADOW...TO SAFFORD...TO SIERRA VISTA. THE 12Z KTUS RAOB STILL INDICATED A DECENT PRECIPITABLE WATER VALUE OF 1.29 INCHES...SIMILAR TO YESTERDAYS VALUES...HOWEVER THE PROFILE SHOWED CONSIDERABLE DRYING TAKING PLACE ABOVE 600 MB. THE MORNING SOUNDING ALSO INDICATED RATHER STRONG WESTERLY FLOW...ESPECIALLY FOR THE END OF JULY. THIS WESTERLY FLOW WILL HELP IMPORT DRIER AIR FROM THE WEST (12Z YUMA SOUNDING HAD .55 INCHES OF PRECIPITABLE WATER) ACROSS MUCH OF THE FORECAST AREA BY TONIGHT. HOWEVER...WITH MOISTURE STILL IN PLACE ACROSS THE EASTERN HALF OF SOUTHEAST ARIZONA AND GENERALLY CLEAR SKIES...EXPECT CONVECTIVE INITIATION TO START OVER THE WHITE MOUNTAINS AND IN THE HIGHER TERRAIN OF GRAHAM AND COCHISE COUNTIES. THE MAIN CONCERN TODAY WILL BE ISOLATED POCKETS OF HEAVY RAIN ACROSS FAR EASTERN PORTIONS OF THE FORECAST AREA...ALTHOUGH THE MOVEMENT OF THE STORMS SHOULD BE QUICK ENOUGH TO ALLEVIATE MOST FLASH FLOODING CONCERNS. ISOLATED STRONG DOWNBURST WINDS WILL ALSO BE A CONCERN IN THE SAME AREA AS MENTIONED ABOVE. STORM MOVEMENT WILL BE TO THE EAST/SOUTHEAST AROUND 15 MPH. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH WEDNESDAY. A VERY LOW-GRADE MONSOON PATTERN IS EXPECTED THURSDAY THROUGH SATURDAY...AS THE RIDGE AXIS SHIFTS OVERHEAD ON FRIDAY AND THEN ALONG THE CENTRAL ARIZONA/NEW MEXICO BORDER BY SATURDAY. DECREASED THUNDERSTORM COVERAGE IS EXPECTED ACROSS ALL OF SOUTHEAST ARIZONA DURING THIS TIME FRAME...WITH THE WESTERN HALF OF THE FORECAST AREA ONLY EXPECTING PARTLY CLOUDY CONDITIONS. A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS WILL STILL BE POSSIBLE ACROSS FAR EASTERN PORTIONS OF SOUTHEAST ARIZONA. AN UPSWING IN THUNDERSTORM ACTIVITY IS THEN FORECASTED LATE IN THE WEEKEND AND EARLY NEXT WEEK AS THE UPPER HIGH SHIFTS NORTH AND EAST OF THE STATE. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. ZELL
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TUCSON AZ
339 PM MST WED JUL 28 2004
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION...ST.. ...SOURCE....
..REMARKS..
0225 PM TSTM WND GST 1 NE TUCSON 32.21N 110.88W
07/28/2004 78 MPH PIMA AZ CO-OP OBSERVER
ROOF OF UNIVERSITY OF ARIZONA ATMOSPHERIC SCIENCES
BUILDING /100FT OFF GROUND/. 1/2 INCH DIAMETER HAIL ALSO
ACCOMPANIED DOWNBURST.
&&
PYTLAKPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TUCSON AZ
457 PM MST WED JUL 28 2004
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION...ST.. ...SOURCE....
..REMARKS..
0248 PM TSTM WND DMG 1 W TUCSON 32.20N 110.91W
07/28/2004 PIMA AZ LAW ENFORCEMENT
POWER LINES DOWNED JUST WEST OF DOWNTOWN TUCSON
0400 PM TSTM WND DMG 3 SW TUCSON 32.17N 110.93W
07/28/2004 PIMA AZ LAW ENFORCEMENT
POWER LINES DOWNED ON SOUTHWEST SIDE. TIME APPROXIMATE.
&&
PYTLAKThe Tucson radar (KEMX), 46 km away, was scanning. The volume nearest the first event began at 00:29 UTC.
2 flash flood. Local standard time, as filed.
County official reported that a 4 foot section of Dusquesne Road was washed out by flood waters.
Law enforcement reported that the road between Topowa Village and Fresnal Canyon were impassible due to high water.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2004Every state in 2004This day in weather historyWarnings in Arizona, July 2004
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: 5415777, 5415778.