‘It could get ugly’: Atmospheric river expected to bring flooding to California

SFGATE – By Amy Graff – Mar 8, 2023

An atmospheric river is forecast to dump rain over California’s massive snowpack Thursday and Friday, raising concerns that a rush of snowmelt at lower elevations could cause flooding. Roadways in the Sierra Foothills are especially at risk for flooding.

“It could get really ugly,” said David Rowe, a meteorologist with the National Weather Service. “Probably most of the melt will be in the foothills. The snowpack is so deep in the higher elevations, even though we’re expecting a lot of rain, it will probably soak right in at the higher elevations.”

There are all types of atmospheric rivers, and this one is an example of a “Pineapple Express” as it’s pulling moisture from near the Hawaiian Islands.

These storms are known for bringing above-normal temperatures in winter, and Rowe said snow levels will probably get up to 8,000 feet in this event. The heaviest precipitation is expected in Northern California on Thursday and Friday, and the warmest conditions are expected Friday afternoon, when valley locations are likely to break into the 60s, and the foothills could see temperatures in the mid-50s. Truckee and Yosemite are expected to hit a high of 42 degrees Friday.

The storm is raising concern as the state has seen a rash of cold storms in recent weeks that brought snow to unusually low elevations across California. Elevations as low as 2,000 to 2,500 feet in the coastal ranges and the Sierra Foothills have a couple feet of snow piled up. These areas are likely to be drenched in warm rain in coming days, and Rowe said that by Friday afternoon most of the snow below 4,000 feet will likely have melted.

“You’re going to have rain falling into the snow, some will fall onto the roads. You’re going to have water running down the roads, the drains could be clogged,” Rowe said. “That’s why we’re recommending avoiding driving. The best window for anyone going up to Tahoe would be to leave early Thursday morning, try to get up there before nightfall tomorrow.”

At higher elevations above 5,000 feet, the Sierra snowpack is the deepest it has been in decades.

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Posted by Teri Perticone


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