For Bay Area, Christmas to have a lot of nasty weather on tap

The door letting in nasty Bay Area weather just in time for Christmas opened a bit wider over the past 24 hours, according to the National Weather Service, and now there is more than just rain, heavy winds and the odd clap of thunder threatening to enter.

Add to the list now the likelihood of severe thunder-and-lightning storms, and perhaps tornadoes.

“Essentially,” NWS meteorologist Dylan Behringer said, “rain is now third on the list of priorities. There’s still gonna be a decent amount, but that’s not what we’re most concerned about.”

Instead, Behringer said the primary worry with this wave of an atmospheric river storm are the southerly winds that are likely to begin blowing Tuesday night and last into Wednesday morning, according to the weather service. Those winds are expected to take a break on Wednesday night, before building again on Thursday’s Christmas morning. The coastal areas of the Bay Area and the Central Coast are most at risk. Behringer said winds there could blow as high as 60 mph.

The weather service issued a high wind warning for the coastal areas of the region and a wind advisory for the interior areas that goes into effect at 4 p.m. Tuesday and lasts until 4 p.m. Wednesday. The weather service expects the winds to be powerful enough to snap power lines, bring down trees and result in property damage.

“When we get into Thursday morning, there will be more of a chance for really strong thunderstorms,” Behringer said. “That will bring lightning strikes, and high-rain rates. Lots of rain coming down really fast can cause flash floods. The good news is that the winds will make the storm move fast, so we don’t anticipate that hard rain coming down in one spot for very long.”

That said, the rain is supposed to pound the region heavily. At least an inch of rain and perhaps more likely 1½ inches are expected everywhere, while high-elevation areas along the North Bay coast could get between 2-3 inches from this wave.

A flood watch for the North Bay began Monday, while a similar warning went into effect for areas south of San Francisco — including San Jose, Santa Cruz and Monterey — early Tuesday. That flood watch for all areas lasts until Friday at 10 p.m.

The weather service also issued an warning for extremely dangerous marine conditions along coastal waters along the Northern California coast that runs from Tuesday until Friday morning. A beach hazards statement also was set to go into effect at 4 p.m. Tuesday for all the beaches on the Pacific Coast. Waves are expected to break at 20 feet high, visibility is expected to be low and people are advised to stay away. The hazards statement will be in effect until 4 a.m. Wednesday.

By Friday night, the wave of nasty weather is expected to have moved into Southern California, and a period of dry, cold time is expected to follow, Behringer said. The forecast is expected to be without rain from at least Saturday until the following Tuesday, and Behringer said forecasters “expect a decent period of drying out.”

“It’s gonna get chilly, too,” he said of the dry period. “The overnight lows will start to drop into the 30s.”