Instability associated with a cut-off upper level low resulted in scattered strong thunderstorms and widespread showers in Southern California on Thursday. A GOES Sounding 8 nm NW of KLAX at 3:00 pm indicated an LI of -4 and CAPE of 836.

According to NWS Storm Reports a spotter in Simi Valley area near Tapo St. and the 118 Frwy reported 1.0 inch of rain in 15 minutes and 1.5 inches in 30 minutes with street flooding. A Mesonet station in Simi Valley recorded 0.84 inches of rain in 12 minutes. A Mesonet station near Pasadena recorded 1.1 inches in 25 minutes. Long Beach Airport set a new rainfall record for the date of 0.30 inches.

The rain gauge at Downtown Los Angeles (USC) dodged all but a few rain drops, recording 0.01 inch for the storm. Here's an archived copy of a NWS compilation of preliminary rainfall totals across the area.

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