California Braces for Rare Blizzard Conditions

Blizzards are not typically associated with Southern California, but residents were nevertheless preparing on Thursday for a potent winter storm that forecasters warned could make mountain roads unpassable.

The National Weather Service in Los Angeles has issued a winter storm warning for the mountains of Los Angeles, Ventura and Santa Barbara Counties until early Friday, warning of “extremely dangerous mountain conditions.” A rare blizzard warning, for the same areas, will take over from Friday through Saturday.

This isn’t the first blizzard warning from the Los Angeles National Weather Service office, but it has been decades since the last one. The office’s records go back only to 2006, so its forecasters, more accustomed to issuing high surf advisories and flash flood warnings, were unsure of their last blizzard warning. After some sleuthing, they found one that was issued on Feb. 4, 1989.

As California braced for its unusual weather, a heavy storm played out in a region far more used to snow: the Upper Midwest, where hundreds of thousands of customers were without power early Thursday, hundreds of schools were closed, and air travel was disrupted.

Forecasters in Los Angeles described the storm affecting that region as a dangerous one, and they predicted up to seven feet of snow in areas more than 4,500 feet above sea level. Lesser amounts, between one and six inches, were expected in elevations of less than 2,500 feet. Areas along the coast and valleys could see up to five inches of rain.

The lower-elevation snow will mean that this could be the largest amount of 24- to 48-hour snowfall seen in decades — likely since a 1989 snowstorm that snarled traffic — for the Ventura and Los Angeles County mountains, forecasters said.

“Everything is adding up for a major snow event,” said Andrew Rorke, a senior forecaster for the Weather Service office in Los Angeles.

A person standing in downtown Los Angeles can see a 10,600-foot peak that will typically have snow on it, Mr. Rorke said. By Saturday that snow will extend much farther down the mountain, showing more snow than a typical winter storm.

But don’t expect the Hollywood sign to be lost in a snow-covered hillside.

“The Hollywood Hills are saved from snow, but the San Gabriels behind the Hollywood sign are certainly not,” Mr. Rorke said.

Los Angeles is surrounded by mountains, and when they get heavy snow, passage through them shuts down.

The California Governor’s Office of Emergency Services issued a news release on Wednesday, detailing numerous ways that Californians should prepare for the storm, including collecting a bag with important documents, cash and medications. Officials also warned against using a gas stove or oven to heat a home.