Sierra travelers trapped by back-to-back storms that dropped more than 2 feet of snow have a brief window to pass before the arrival of a weather system Saturday so wet forecasters are calling it an “atmospheric river.”

Up to 12 inches of rain below 8,500 feet is expected, and massive amounts of snow — up to 6 feet — above that elevation. A fourth, colder storm two days behind will drop yet more heavy snow.

“It’s a once-in-10-year event,” said Zach Tolby, a meteorologist with the National Weather Service in Reno. “It’s the strongest storm we’ve seen in a long time, the kind of setup we look for to get significant flooding.”

The atmospheric river, or “Pineapple Express,” will be felt across much of California this weekend, though rains will be much heavier in the north than in the south.

Tolby said the storm is packing the same wallop as an atmospheric river that hit Northern California a decade ago that caused $300 million in damage, according to the U.S. Geological Survey. ……

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