More Powerful Of Back-To-Back Storms Poised To Slam NorCal

SAN FRANCISCO — The Bay Area will have little time to dry off before the next atmospheric river hammers California, and forecasters warn the incoming storm may prove stronger than the last.

The new system arrives in the wake of the last atmospheric river, which doused parts of the North Bay with more than 4 inches of rain between Wednesday and Thursday and deposited at least two inches over portions of the Peninsula, South Bay and East Bay.

As winds kicked up Thursday morning, a video showed an apparent funnel cloud touching down in unincorporated Sonoma County near Petaluma.

Now, the National Weather Service is tracking a "rapidly strengthening" low-pressure system, as a deep well of subtropical moisture mixes with cold air from the northwest, which forecasters predict will bring more heavy rain and widespread wind gusts as high as 50 mph.

Even as forecasters see the brunt of the rainband slamming the Central Coast, the storm is poised to dump another 3 to 5 inches of rain at higher elevations of the North Bay, San Mateo, San Benito and Santa Clara counties between Saturday night and Monday, with storm activity peaking Sunday.

San Francisco, Oakland, and the East Bay hills could see 2 to 3 inches, along with the interior North Bay and lower elevations of San Mateo County. Another 1 to 2 inches is forecast for the Santa Clara Valley and interior East Bay.

The weather service has issued a new flood watch to take effect across the region Saturday afternoon through Monday morning, and wind advisories or warnings will be in place throughout Sunday.

"Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations," the weather service said. "Flooding may occur in poor drainage and urban areas. Low-water crossings may be flooded."

Strong gusts will again play a major role in the storm, triggering a high wind advisory for a large swath of the Bay Area and wind advisories in the North Bay, San Francisco and portions of the East Bay and Peninsula.

"Confidence is strong that this will be as much of a wind event as it is a rain event," the weather service said Friday. "The strongest winds will favor the southern counties of the [forecast area] along with the San Mateo Coast, Santa Cruz Mountains, and higher portions of the East Bay. The current forecast calls for even stronger winds than the previous storm system specifically for those areas."

In the mountains, forecasters expect snow to pummel the Sierra for several days, beginning with up to 18 inches at Donner Pass by the end of Friday night. According to the San Francisco Chronicle, 2 to 3 feet of fresh snow could fall in the Northern Sierra, including around Lake Tahoe, by the storm's end.