May 19, 2023
An upper-level low pressure system situated near the northern Baja Peninsula aided in bringing in abnormally high moisture content into south-central and southwest AZ. Precipitable water values of approximately 1 were observed, which for mid-May is a record. MLCAPE values of around 500 J/KG were also observed. The combination of the moisture and instability resulted in the development of an intense cluster of thunderstorms across the higher terrain zones northwest of Phoenix during the afternoon
Source: NOAA National Weather Service Storm Events Database (event 1100674). Narrative written by NWS staff at the time of the event.
This event is one of many recorded floods in Maricopa County. See the full FEMA flood zone map, NFIP claim totals, and disaster history for the area.