Aug 31, 2017
A large upper level ridge of warm air over the Great Basin brought persistent east to southeast flow over the region in late August. Strong flow and limited instability largely kept the convection below severe levels. However, weakening of the ridge on the 31st increased instability. This helped severe convection develop over the Inland Empire. Downburst wind intensity was aided by dry air in the low levels and record high temperatures.
Source: NOAA National Weather Service Storm Events Database (event 720733). Narrative written by NWS staff at the time of the event.
This event is one of many recorded floods in Riverside County. See the full FEMA flood zone map, NFIP claim totals, and disaster history for the area.