Strong winds, flooding expected as Bay Area rain likely through Monday

As wet and as windy as the arrival of the new year was on Thursday, it was likely only a fraction of what the National Weather Service anticipates will happen when the main front of the next storm system hits the Bay Area.

The next one is forecast to start dropping rain and producing southerly winds that may be in excess of 50 mph in some regions beginning Friday night and create serious flooding near areas close to the coast. The storm is expected to last well into Saturday.

“The bulk of the main front is expected to move through Saturday morning,” NWS meteorologist Roger Gass said. “That’s when we expect the winds to really kick up.”

As for the flood threats, the weather service said the rains combined with king tides created by the position of the moon could create a high tide that is 2½ feet higher than normal, a scenario the weather service said it hasn’t recorded since 1988.

The weather service issued a coastal flood warning along the San Francisco Bay Shoreline that’s in effect through 2 p.m. Saturday.

The higher tides than normal will be crashing amid possible isolated thunderstorms, too, Gass said.

“The air mass is going to be colder in the system that’s coming behind the one that’s arriving Friday,” Gass said. “So generally, there’s probably 15% to 25% chance of thunderstorms, and I wouldn’t be surprised if there are some funnel clouds.”

The winds are expected to blow in a southerly direction, typical of an atmospheric river storm. Gass said they are likely to drop trees and create power outages but “that they’re not going to be nearly as strong as what we experienced during the Christmas holiday.”

In the Sierra Nevada, the weather service expects heavy snow and upgraded a winter storm watch into a winter storm warning for elevations above 5,000 feet. That warning begins at 10 p.m. Friday and runs through 4 p.m. Monday. The weather service said they expect 6-to-12 inches of snow above 5,000 feet and 2-4 feet of snow above 6,000 feet. Winds in that area are expected to gust up to 55 mph.

The rain that fell Thursday came down in sheets at times and in a slow drizzle at others. In the 24 hours ending at 7 a.m. the weather service recorded about 1 1/2 inches at Mt. Umunuhum and 1 1/4 inches at Valley Christian, both in Santa Cruz County. About three-quarters of an inch fell in Mill Valley in Marin County; a half-inch fell in San Francisco, a quarter-inch fell at the Oakland San Francisco Bay Airport, one-tenth of an inch fell in Concord and seven-hundredths of an inch fell in San Jose.

“We didn’t get much rainfall overnight,” Gass said.

The rain is likely not to clear entirely until Monday afternoon or evening, according to the weather service. Gass said another round of possibly heavier rain is expected later Saturday afternoon into Sunday, and that another storm cell is possible for early Monday.