The Bay Area’s second atmospheric river storm of the winter announced its presence early Saturday with methodical and intense power, and weather forecasters advised residents to settle in for several hours of it.
Hard sheets of rain and hard winds ripped through much of the region through the overnight hours past sunrise, according to the National Weather Service. Those areas that remained somewhat dry were expected to receive their downpours later Saturday.
Flood advisories in Alameda and Contra Costa counties were in effect until 8:30 a.m; a flood advisory remained in effect in San Jose until 11 a.m.; and Santa Cruz County had a flood advisory in effect until noon.
Wind advisories also remained in effect through the entire region. Wind gusts whipped up to 63 mph at Loma Prieta in the Santa Cruz Mountains; 60 mph the Black Diamond Mines in Antioch; 55 mph in the Peninsula; and 50 mph in Livermore.
“It’s what we expected,” NWS meteorologist Ryan Walbrun said. “We don’t expect it to stall or lose strength. It’s moving steadily.”
The storm, as expected, was having its most powerful impact in the mountains and hills. By 7 a.m. Saturday, about 5¼ inches of rain had fallen over a 24-hour period in Ben Lomond in the Santa Cruz Mountains and more than 3½ inches fell over the same time on Mount Diablo in Contra Costa County.
Oakland received just shy of 2½ inches of rain, as did Danville. About 1.9 inches fell at the San Francisco Airport, 1½ inches fell in Richmond and 1¼ inches fell in Walnut Creek and Concord. All of the rainfall totals were from the previous 24 hours.
San Jose received less than an inch of rain overnight, while an area near Coyote Creek received barely more than a half-inch. Those areas were expected to be hit harder later Saturday.
“The main part of the rain is pretty much over most of the Bay Area, and the areas from Marin, Alameda and Contra Costa (counties) were getting the brunt of it,” Walbrun said. “We expect it to stay that way roughly through noon to 2 p.m., then it will shift more toward the South Bay and the Central Coast.”
Flooding caused all lanes on southbound Highway 17 to be closed near the Alma College Road exit, according to the California Highway Patrol. At 8 a.m., the agency’s log showed 91 incidents on Bay Area freeways, many of them minor vehicle collisions caused by the rain.
The rain will clear out of the region by Sunday, Walbrun said. But the appearance of the sun will be only a brief one, with more light rain expected on Monday before a third atmospheric river storm bears down on the region.
“We’re already watching that one,” Walbrun said.
That third storm is expected to arrive by Wednesday.