Monsoon moisture in place over the region may lead to numerous thunderstorms. Photo via Pexels

 A flash flood watch for San Diego County mountains and deserts was issued by the National Weather Service Saturday between 11 a.m. and 11 p.m.

Excessive runoff may result in flooding of rivers, creeks, streams and other low-lying and flood-prone areas, the NWS said. Monsoon moisture in place over the region may lead to numerous thunderstorms, especially during the afternoon and evening hours.

“You should monitor later forecasts and be prepared to take action should flash flood warnings be issued,” forecasters said. “If you come across a flooded roadway, turn around, don’t drown.”

A beach hazards warning was also issued from 8 a.m. Saturday through the weekend for coastal areas. Possible thunderstorms Saturday through Sunday afternoon were expected, which could bring dangerous cloud-to-ground lightning.

Elevated surf of 4 to 6 feet may develop Sunday night and continue through Wednesday, the NWS said. The elevated surf and strong rip currents could create dangerous swimming conditions.

High temperatures along the coast Saturday were predicted to be 72 to 77 degrees with overnight lows of 62 to 67. Highs in the western valleys were expected to be 80 to 85, and 87 to 92 near the foothills with overnight lows of 62 to 67. Highs in the mountains were expected to be 84 to 90 with overnight lows of 62 to 69, and highs in the deserts were predicted to be 101 to 106 with overnight lows of 79 to 85.

Slow drying of the atmosphere may begin on Sunday and could continue through Tuesday, but sufficient moisture and instability continue to support afternoon thunderstorms, gradually becoming more tethered to the mountains and high desert areas as winds turn more southerly.

–City News Service