By Jim Purpura. Posted July 31, 2012, 10:46 AM.

The strongest monsoon surge of the year has brought thunderstorms with frequent lightning and locally heavy rain, and flash flooding to the mountains of San Bernardino, Riverside, and San Diego Counties yesterday. More of the same is expected today, as a Flash Flood Watch is in effect for mountain areas.

A closed circulation system, actually a small low pressure area embedded in the monsoonal flow is bringing moisture from the Gulf of Mexico and helping lift the air, forming the showers and storms.

Most of the WeatherCurrents network was not affected, but our Cherry Valley station, at almost 3000 feet elevation in the Banning Pass, did record 0.24 inch of rain Monday.

Other significant totals, courtesy of the National Weather Service, and Weather Currents observers...

Cameron (San Diego County) 2.09 inches

Octotillo Wells (San Diego County) 2.02 inches

Campo (San Diego County) 1.66 inches, all in 1 hour

10 east of Julian (San Diego County) 1.16 inches, all in 15 minutes

Cuyamaca Lake (San Diego County) 1.08 inches

Anza (Riverside County) 0.82 inches