Heavy rain and persistent winds blew over the Bay Area over the weekend, prompting evacuations, flooding roads, and knocking out power for thousands of residents.
On Monday, authorities lifted evacuation orders in San Mateo County for a few South Coast communities in the CZU Lightning Complex fire burn zone, including areas near Loma Mar and Butano Creek State Park. The National Weather Service also lifted its wind and flash flood advisories. The Temporary Evacuation Point set up by the county and Cal Fire at the Ted Adcock Center in Half Moon Bay is now closed.
More than 4.55 inches of rain fell in Half Moon Bay over the past 48 hours, according to the National Weather Service. That was moderate compared to elsewhere in the region. In the North Bay, Mount Tamalpias recorded 16.55 inches in the same span.
The rain came in the form of the first atmospheric river of the season. The phenomenon are long narrow bands of concentrated water vapor that can hold as much water as in the Amazon river. They begin in the warm waters of the Pacific when water evaporates into the air. When that warm air hits a Pacific storm, the result is a concentrated rain event. Once the concentration of vapor meets the coastal range and the Sierras, ever more water is squeezed out of the system. As much as half of all California precipitation comes from atmospheric rivers.
On the Coastside, several residents posted images and videos on NextDoor of fallen trees that took down power lines and closed streets. In Pacifica, power remained out for much of the Sharp Park neighborhood, affecting at least 500 customers as well as a few residents in Linda Mar, according to PG&E’s outage map. Some structures in El Granada and Moss Beach remained without power as of Monday afternoon.
It was a historic storm in terms of rainfall. Golden Gate Weather Services estimated about 4.02 inches of rain fell in San Francisco on Sunday, making it the fifth-wettest day in the city for the last 172 years. The consulting company stated that the weather event was the region’s third-largest storm according to its Bay Area Storm Index. The index rates a storm’s power based on factors like sustained rain, wind and gusts. Sunday’s rainfall was scaled as a 9.7 out of a possible 10.
All that rain swamped some of the coastal infrastructure. The Pacifica Police Department cordoned off Highway 1 in both directions at Manor Drive for a time on Sunday. About a foot of water stood on part of Pescadero Creek Road, according to Cal Fire spokeswoman Cecilie Juliette. The hazardous road conditions on Sunday sent emergency personnel scrambling. Cal Fire crews from the Felton Emergency Command Center responded to 124 incidents over 24 hours on Sunday in San Mateo and Santa Cruz Counties. That’s nearly five times the 25 to 30 average number of responses.
While meteorologists say that the worst of the storm appears to have passed, the National Weather Service’s High Surf Warning issued on Friday remains effective until 11 a.m. on Tuesday.