As the week long event continued, the upper level disturbance located near the four corners became much better defined with water vapor imagery indicating this feature became a closed upper level low pressure system. The dynamics from this upper level low in addition to an area of diffluence aloft between the upper level low and an inverted trough over Northwest Mexico/Western Texas would yield another night and morning of excessive rainfall across Southeast Arizona due to elevated convection. Precipitable water from the 00Z July 28 KTUS sounding was 1.63".

Early in the evening the first thunderstorms developed over the Gila Mountains of Southwestern New Mexico and pushed southwest into Greenlee County. This complex of thunderstorms continued to push southwest as the evening wore on through Graham, Cochise and then into Southeast Pinal and Eastern Pima county around midnight. As the thunderstorms moved through portions of Greenlee County and Graham County, 1 to 3 inches of rain fell in the time span of a couple of hours causing flash flooding through portions of both Greenlee and Graham county. As this complex of thunderstorms pushed through Eastern Pima and Southeast Pinal County, it lost some of its punch but not before dropping over an inch of rain across the Santa Catalina Mountains just north of Tucson.

There was still more to come from two complexes of thunderstorms to move across Eastern Pima County through midday July 28th. The first complex developed over the Mogollon Rim around midnight, likely due to another disturbance coming around the upper level low. The heaviest rainfall from this wave hit across Southeast Pinal and across the northwest side of the Tucson Metropolitan Area between 1:30 am and 3:00am. Observed totals from this round were generally less than one half inch across the Tucson metropolitan area. This MCS then continued to move into Central Pima County before weakening around sunrise. After 7 am, another complex of thunderstorms over Graham County became better organized as it pushed southwest toward the Tucson metropolitan area. This thunderstorm complex dropped another inch of rainfall over portions of the Santa Catalina mountain range. The first reports of river flooding from this event occurred along the Santa Cruz River in a couple of housing developments in Eloy during the afternoon of July 28th.