Atmospheric river expected to slam into area Sunday

Bay Area residents should gear up for a week of travel delays and possible flooding with the tail end of an atmospheric river slated to hit Northern California this weekend, followed by a soggy, windwhipped Christmas holiday.

A “Pineapple Express” system will crash into the Pacific Northwest starting this evening, drenching the Washington-Oregon border as it moves east from Hawaii, according to the National Weather Service. Though Northern California will likely avoid the worst of the deluge, the region is expected to see about 12 hours of rain starting sometime between midnight and late Sunday morning.

“Hopefully it comes through earlier because there will be a

lot of people traveling this weekend,” said Spencer Tangen, meteorologist with the NWS. “That’s one of our biggest concerns with this storm.”

By the time it passes, the weather system — an atmospheric river named for its tropical origin — is forecast to bring about 2½ inches of rain to the North Bay and Santa Cruz mountains; in San Jose and Oakland, meanwhile, totals will hover closer to a half-inch.

With the exception of possible flash floods on the Kincade fire burn scar in Sonoma County, major flooding is not expected, Tangen said, though the rainfall will trigger slick roads and bad visibility. Winds also will reach about 10 to 15 mph, with gusts up to 25 mph, likely leading to flight delays at San Francisco International Airport.

Already, low-hanging clouds prompted SFO to initiate a ground delay program on Friday morning, delaying 256 flights and canceling another 30 by midday, spokesperson Maria Buyco said.

But it’s too early to tell what’s in store for the weekend and beyond, she said.

“The best advice is to check with your individual carrier because it will vary depending on the time of the flight and the carrier,” Buyco said.

Similarly wet and windy conditions are expected across the state, with up to 12 inches of snow predicted for the Sierra Nevada elevations above 4,500 feet, covering an area stretching from Sonora Pass to Lassen Park. And as the rain dries up in the Bay Area Sunday night, the Pineapple Express will move southeast, bringing rain — and travel chaos — to Southern California Monday and Tuesday.

Christmas Eve will likely be the lone dry day in the Bay Area next week, before another storm system comes ashore on Wednesday, bringing an expected half-inch of rain in San Jose and Oakland and at least an inch in the North Bay and Santa Cruz hills.

Christmas Day’s expected high is 52 degrees across San Jose, Oakland and San Francisco, and 48 degrees in Santa Rosa.

As usual, California Highway Patrol’s San Jose unit will increase enforcement over the holiday in effort to deter drunk driving, Officer Ross Lee said Friday. But this year, the agency is also bracing for bad driving conditions as a result of the holiday weather.

“If you’re doing extended traveling or going to see family, please make sure your vehicle’s in good working condition, that you have a full tank of gas, that your lights work and that you have a phone charger,” Lee said.