Cold front blowing into region likely to set record lows

A week for warm layers and oversize winter jackets has arrived as a frigid storm stomped its way into Northern California and the Bay Area on Sunday, bringing with it record-breaking cold temperatures and snow to the Sierra, forecasters said.

Travelers heading to the mountains during the President’s Day holiday weekend should expect dicey and icy driving conditions. The first wave of the winter weather system brought snow to the Interstate 80 and Highway 50 mountain passes on Sunday afternoon.

Chain controls were in effect as the storm caught many drivers off guard, causing several crashes near Donner Pass, Caltrans officials said.

Lower elevations were not spared from the freezing burst as the chilly, blustery front spread throughout the Bay Area and beyond. Temperatures are only expected to get colder, bottoming out to a freezing chill on Tuesday morning, said Drew Peterson, a meteorologist with the National Weather Service.

“It takes a little time for the coldest air to get here,” Peterson said.

As a bracing precursor to the frigid temperatures, cold northwest winds kicked into high gear Sunday, with wind speeds up to 25 mph and gusts up to 40 mph.

Bay Area temperatures may start plummeting below freezing as soon as Monday night, Peterson said.

San Francisco is expected to break records Tuesday morning by dropping to 38 degrees. It’s small comfort to note that despite the brisk air, San Francisco will probably still be one of the warmest cities in the Bay Area that day.

“No matter which way you go north, east or south, temperatures are going to be colder than downtown San Francisco,” Peterson said.

Homeless shelters in San Francisco are expanding their capacities during the cold snap, and street outreach workers will be offering extra blankets and transportation to shelters, city officials said.

On Monday night and Tuesday morning, the North Bay is forecast to drop to the mid-20s. The East Bay is looking at temperatures in the 20s to low 30s, and 30-degree marks are anticipated in the South Bay.

Temperatures in Morgan Hill and Gilroy are expected to be below freezing, in the upper 20s.

The weather service has issued a freeze warning for the Bay Area from Monday night to 9 a.m. Tuesday, with residents advised that the subfreezing temperatures could harm crops, vegetation and animals.

With the chillier forecast, some snow could dust the highest peaks of the Santa Cruz Mountains and Big Sur, forecasters said.

There may also be some precipitation over the coastal North Bay mountains, including Mount Tamalpais, but it’s too early to tell, Peterson said. Either way, don’t count on a lot of rain.

“This is a very cold, but dry system,” Peterson said. “This is not going to be a big snow producer for the Sierra, mainly because there’s not a lot of moisture.”

Nevertheless, snow was already falling at higher elevations in the Sierra — which has seen a near historic low snowpack this year.

By Wednesday, the cold snap should begin to ease — but just a bit.

“It’s a constantly evolving situation,” Peterson said. “Wednesday will be pretty cold too, but not quite as cold.”

Temperatures might warm Thursday and into the weekend, though forecasters say it’s unlikely to be as warm as it’s been in recent weeks.

“We are going to see a warming trend,” Peterson said. “To what extent, that’s up for debate.”