The active weather pattern continued late July 26th into July 27th as this long event transitioned from the typical diurnal thunderstorm activity usually seen during the monsoon season to a nocturnal enhancement of activity. The early morning of the 27th was the first of five nights with Mesoscale Convective Systems (MCS) developing over the Mogollon Rim and moving southwest into the lower elevations.

The synoptic pattern early in the morning on the 27th showed an area of high pressure aloft over California with relatively strong north to northeast flow with the exception of the lowest levels through 200mb. Late on the 26th, an MCS developed over the Mogollon rim from a weak disturbance in the north to northeast flow around the high pressure aloft. This MCS caused flash flooding in Clifton (Greenlee County) along Ward and Limestone Canyons, Several feet of water flowed through the Canyons. As the night progressed, the MCS continued to push south and west through the rest of Southeast Arizona. Early morning Tucson WSR-88D imagery clearly showed a distinct circulation from a Mesoscale Convective Vortex within the MCS.

The heaviest rainfall was concentrated across Southwest Cochise County, Santa Cruz County, Southeast Pinal County and North Central Pima County with some locations receiving 2 to 3 inches of rainfall. The city of Tucson was generally spared in this event with most locations receiving about one quarter of an inch.