'I wouldn't drive over the Sierra': Weather Service warning for Wednesday and Thursday

Caltrans crews monitor chain control over a Sierra Nevada highway. Caltrans crews monitor chain control over a Sierra Nevada highway. Photo: Caltrans Photo: Caltrans Image 1 of / 38 Caption Close 'I wouldn't drive over the Sierra': Weather Service warning for Wednesday and Thursday 1 / 38 Back to Gallery

A potent storm is forecast to sweep into the northern Sierra Nevada Wednesday afternoon and dump huge amounts of snow, crippling traffic on mountain roads and over passes into Thursday.

The National Weather Service has issued winter weather advisories for the Tahoe Basin and western Nevada for 4 p.m. Wednesday through early Friday morning and warns blizzard conditions and road closures are possible at higher elevations.

Snow levels are expected to drop as low as 5,500 feet and isolated wind gusts could reach 50 to 60 mph.

"I wouldn't drive over the Sierra," warned Karleisa Rogacheski, a meteorologist with the NWS Sacramento office.

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The NWS is still running models to determine projected snowfall totals for the 24-hour period running from Wednesday to Thursday, and Rogacheski expects them to be impressive. This system is a so-called "atmospheric river," with a long moisture plume stretching across the Pacific Ocean.

"Some of these grids have almost a foot or two of snow arriving within six-hour windows," Rogacheski.

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Snow was falling in the Sierra Tuesday morning with a weaker system set over the area, and the scattered flurries are expected to continue up until the big storm hits. A winter weather advisory is currently in effect warning motorists of slick roads and chain control.

Rogacheski expects the first window for safe travel in the Sierra to arrive Friday morning when skies will clear. Dry conditions are also forecast for Saturday, and the potential for snow returns to the forecast Sunday.

"The models are split right now," she says. "Some are showing dry Sunday morning, and some show it wet. You'll want to check the forecast and the Caltrans website before hitting the road."