Flash Flood in Gila County, Arizona

Video showed very fast flowing water along Repply Avenue in Miami. No damages or injuries reported.

A nearly stationary upper-level trough combined with tropical moisture remnants from Tropical Storms Priscilla and Raymond, which developed off the eastern Pacific, led to scattered to widespread thunderstorm activity across much of south-central AZ. Beginning late on the 8th through the 9th, very anomalous moisture from Tropical Cyclone Priscilla surged northward with PWATs rising to over 1.5+, which was an all-time record for early October. Light to moderate rainfall developed, with the most widespread activity occurring from the afternoon of the 10th into the early afternoon of the 11th. Even though rainfall rates were light with no flooding occurring with this initial activity, it saturated the soils for the heavy rainfall that would develop hours later.

Heading into the pre-dawn hours on the 12th, another moisture surge, this time from the remnants of Tropical Cyclone Raymond, combined with strong upper-level ascent from the aforementioned low pressure system off the west coast to trigger scattered thunderstorm activity across much of south-central AZ during the morning and early afternoon hours. With MLCAPE values having increased to around 1000 J/KG, the environment was conducive to high rainfall rates in excess of 1-2+ an hour. These high rainfall rates falling on top of saturated soils resulted in numerous instances of flash flooding across much of south-central AZ.

Another round of scattered thunderstorm activity developed during the afternoon hours on the 13th. With MLCAPE values peaking at 1000 J/KG and deep-layered shear values approaching 50 kts, the environment became conducive for the development of severe thunderstorms, including supercells. One such supercell affected the Chandler, Tempe, and Scottsdale areas with the city of Tempe being severely hit with extensive wind damage from large, mature trees uprooted or snapped, some of which damaged buildings and vehicles, to downed powerlines, and roofs blown off buildings. A damage survey conducted by some NWS Phoenix Meteorologists supported wind gusts with this supercell peaking around 80-90 mph. Other storms that developed through the afternoon and early evening resulted in large hail and more instances of flash flooding. By the end of the multi-day event, rainfall totals ranged between 1.00-1.50' across the Phoenix West Valley to as high as 3.50-4.50' across the Phoenix East Valley, with locations across the foothills and higher terrain areas observing total amounts of 2.50-6.00'.