SAN FRANCISCO (CBS SF) — A storm front lit up the skies with lightning over the Pacific early Monday as it edged toward the San Francisco Bay Area.

Forecasters said light showers would begin over the North Bay late Monday with the main event would move across the Bay Area on Tuesday and Wednesday.

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The front was fueled by cold, unstable air driven south by the jet stream that gave birth to quite a lightning storm over the Pacific off the Northwest coast.

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“As the cold air aloft moves in overhead on Tuesday instability increases at the surface and aloft,” forecasters said. “Therefore, thunderstorms will be possible with greatest threat during the day Tuesday afternoon. Main threats with developed cells will be heavy rain, gusty winds, small hail, and lightning. Given the lower snow levels hail could accumulate rather quickly in stronger cells.”

The weather service added that there was “a decent likelihood for a (lightning) strike or two.”

The cold temperatures will also drop snow levels to 3000-3500 feet during the day on Tuesday. Snow will be likely over the higher terrain.

The approaching storm was also kicking large, dangerous swells along the Northern California coastline. The National Weather Service has issued a hazardous beach warning until 7 p.m. Monday with northwest swell of 13 to 16 feet at 14- to 16-second intervals.

“Increased risk of hazardous large breaking waves in shallow water along unsheltered coastlines, stronger rip and longshore currents,” forecasters warned.

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The warning spanned ocean beaches including Point Reyes National Seashore, the San Francisco Peninsula coast, Southern Monterey Bay and the Big Sur coast.