Storm to bring snow to Sierra, chill to Bay Area

“It looks like after that rain passes, it could get chilly again.”

The first significant storm of the winter season will pour more snow on the Sierra this week, possibly forcing road closures, according to the National Weather Service.

Meteorologists warn that conditions could become dangerous for motorists heading into the mountains, with low visibility on roads and a possibility of whiteouts late Wednesday and Thursday.

A cold front will sweep into the Bay Area and Sacramento

Valley, bringing the first wave of rain and snow showers into Northern California on Wednesday. These showers will become more widespread by Wednesday night into Thursday as they seep into Santa Rosa, San Francisco and Oakland. Prevailing northwest winds will then steer moisture from the Pacific Ocean toward the Sierra Nevada.

By Thursday, total whiteout conditions will be possible in the Tahoe area and Donner Pass, with heavy snowfall over the Interstate 80 corridor between Reno and Auburn. Look for more than 2 feet of snow between 1,000 and 2,000 feet and 3 to 4 feet of snow above 7,000 feet.

Bitterly cold air will settle over most of Northern California beginning Tuesday night and continuing through the week. North Bay residents are expected to face the coldest temperatures but large swaths of the Bay Area will be waking up to freezing temperatures. Overnight lows Tuesday and Wednesday in Santa Rosa, for example, will dip down to around 30 degrees.

The chilly weather is due to a cold front moving through and bringing with it cold, dry air from the north. This dryness is part of the reason why it will be unusually cold in the coming days. Moist air — like clouds — can act like a blanket that keeps the Earth’s surface warm after sunset by trapping in heat.

“With a drier air mass, more of that heat is able to escape,” Sarah McCorkle, a meteorologist with the National Weather Service’s Bay Area office said.

If enough cold air seeps into the Diablo Range by Thursday night, residents in San Jose could see snowcapped mountains Friday morning.

Low temperatures should be higher Wednesday night into Thursday morning, when a storm system moves in. The global weather models — the European, Canadian and American — are projecting anywhere from an inch to an inch and a half of rain across the Bay Area on Thursday. A few pockets along the western flanks of the Sonoma and San Mateo County mountains, the Diablo Range and the Santa Cruz Mountains could see as much as two and a half inches of rain before all is said and done.

For those hoping that what has been an abnormally cold November might finally be over are likely going to be disappointed.

“It looks like after that rain passes, it could get chilly again,” McCorkle said.