Flood in Pinal County, Arizona

Several roads across the city of Maricopa had standing water from the multiple hours of rain that fell between 12:30 am and 5 am MST. Doppler radar as well as rain gauges measured total rainfall amounts in excess of 2 inches throughout the entire time span. Flooding overall was minor. No damages or injuries were reported.

The combination of the subtropical high pressure over Colorado and an upper trough over west coast led to south-southwest flow over much of the region. Thunderstorm activity during the afternoon hours developed across southwest Maricopa County as well as across the Mogollon Rim area. By the mid to late evening hours, colliding outflows from these storm complexes led to the development of additional thunderstorm activity across the Phoenix area, especially across the central and northern portions of the metro. With MLCAPE values between 500-1000 J/KG and DCAPE values near 1500 J/KG, conditions were favorable for these storms to produce strong to locally severe wind gusts. In addition, the thunderstorm activity due to very light steering flow was also slowing moving, leading to a flash flood threat with some areas in the heaviest activity measuring in excess of 1-2 inches of rain in a short time span. Additional thunderstorm activity continued into the overnight period with coverage becoming more widespread across much of south-central AZ as leading shortwave trough originating from the main upper-trough over the west coast helped to sustain the activity. Some areas across northwestern Pinal County, including the City of Maricopa, measured rainfall amounts in excess of 2 inches in a 3-5 hour time span, resulting in some flooding issues.