High pressure over the Southwest was predicted to bring increasing monsoonal moisture to Southern California this weekend, the National Weather Service said.
Thunderstorms were possible, mainly in the mountains and deserts Sunday afternoon and evening, the NWS said. Showers may drift across the coastal and valley areas Saturday night into Sunday morning.
A Flash Flood Watch was issued for Riverside and San Diego County mountains from noon until 7 p.m. where most insense storms are expected, NWS said. Gusty winds and hail were also possible with stronger storms.
A line of showers and thunderstorms moved across the county during the early morning hours with frequent lightning and brief heavy rainfall, NBC 7's Meteorologist Crystal Egger said.
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Marine layer clouds may be more limited due to the monsoonal flow and higher sea surface temperatures. This pattern was expected to also favor higher humidity and warmer nights.
Sunday's highs were expected to be the mid to upper 70s on the coast, mid-80s inland, mid-80s in the mountains with isolated evening thunderstorms, and 105 with isolated PM thunderstorms in the deserts.
The best chances for thunderstorms look to be Sunday afternoon, the NWS said.
Periods of isolated to scattered showers and thunderstorms may be seen much of the coming week as a weak monsoonal flow continues.
High temperatures were predicted to be near seasonal summer norms next week, but nights may be a little warmer than normal.
Night and morning low clouds at the coast were predicted to be more patchy and intermittent.