A very wet and rather unstable airmass was in place across southern Arizona on the 4th of July. A weather disturbance moving into southern Arizona from Mexico led to scattered showers and thunderstorms across portions of south central Arizona during the morning hours. A cluster of thunderstorms over western Pinal county led to locally heavy rainfall in the area around Casa Grande; 3 hourly rainfall totals in excess of 1.5 inches were observed. This led to urban flooding, especially in the community of Arizona City.

Heavy Rain in MARICOPA, ARIZONA
From 04-JUL-12 11:15:00 to 04-JUL-12 12:30:00 (MST-7)
Location: WADDELL
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Scattered showers and thunderstorms containing locally heavy rainfall developed across south central Arizona during the morning hours on July 4th, and they affected the greater Phoenix area. A trained weather spotter in Surprise, near the intersection of Greenway and Reems roads, indicated that approximately 1.5 inches of rain fell between 1115 am and 1230 pm. Nearly three quarters of an inch fell in 45 minutes, and the heavy rain flooded their yard.

Heavy Rain in PINAL, ARIZONA
From 04-JUL-12 08:30:00 to 04-JUL-12 11:30:00 (MST-7)
Location: ARIZONA CITY
Property damage: 250.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A cluster of thunderstorms developed in the area from Casa Grande southeast to Arizona City; the storms produced locally heavy rainfall during the late morning hours on July 4th. Radar estimates, as well as surrounding rain gage reports, suggested that three hourly totals between one and two inches occurred in the community of Arizona City between 9 am and noon. A weather report received via CoCoRaHS indicated 1.05 inches of rain fell in Arizona City, as of 9 am. Pinal county law enforcement reported road closures in Arizona City due to heavy rainfall. According to a local news report, a number of residents of Arizona City experienced significant urban flooding during the morning due to the heavy rains; water up to a foot deep flooded their subdivisions and flowed into their homes, causing water damage to the first floor as well as their patios/pavers. Insufficent drainage allowed the locally heavy rains to quickly pond up across the lower elevations of Arizona City, and the water levels remained high through the afternoon hours.

Heavy Rain in PINAL, ARIZONA
From 04-JUL-12 09:00:00 to 04-JUL-12 11:30:00 (MST-7)
Location: STANFIELD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

According to the Santa Rosa @ SR 84 Maricopa County Flood Control District gage, 1.54 inches of rainfall were observed a in 3 hour period ending at 11:30 AM on the 4th of July. Similar values were observed at a nearby gage to the east, Santa Cruz @ SR 84. Both gages were located along State Route 84, between the communities of Stanfield and Casa Grande. The heavy rainfall caused the Santa Rosa wash to run heavily. Water ponding on State Route 84 caused the temporary closure of the road during the late morning and early afternoon hours. No accidents were reported on SR 84. The heavy rain was produced by a cluster of thunderstorms that developed ahead of a weather disturbance approaching from northwest Mexico.

Heavy Rain in PINAL, ARIZONA
From 04-JUL-12 09:00:00 to 04-JUL-12 11:30:00 (MST-7)
Location: CASA GRANDE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Scattered to numerous showers, and isolated thunderstorms, developed across south central Arizona during the morning hours on July 4th, and they produced locally heavy rain which affected the communities of Casa Grande and Maricopa. Based on radar estimates and surrounding rain gage reports, rainfall in excess of one inch fell within a 3 hour period ending by 11:30 am.  At 9:30 am, the Casa Grande Fire Department/Rescue reported local street flooding in Casa Grande with water 3-4 inches deep over area roads. Local media reported road closures from Murphy Road to White and Parker Road along the West Maricopa-Casa Grande Highway southeast of Maricopa, due to the locally heavy rainfall.