In Sierra Nevada, atmospheric river storm creates ‘chaotic forecast’

A potent ‘atmospheric river’ approaching California on Tuesday morning is creating a “chaotic forecast” for meteorologists with the National Weather Service in Reno who are working to determine impacts from the storm, including snow levels.

Zach Tolby, a meteorologist with the weather service, said the forecast has been difficult because weather scientists are dealing with two storms merging into one.

“There’s a bunch of warm, subtropical moisture coming into California and the Sierra,” Tolby said Tuesday morning. “At the same time, cold air is dropping in from the Gulf of Alaska. With those two things meeting somewhere around Central California, it is creating a lot of challenges.

“Is one going to push the other away? Is warm moisture going to dominate? It’s creating a lot of challenges for precipitation amounts and snow levels.”

Monday afternoon, the weather service in Reno was still working to project snow levels from the storm, which is pulling in warmer tropical moisture from the Pacific Ocean. At one point Monday, meteorologists said snow levels in the Sierra Nevada could rise as high as 8,000 feet.

Tuesday morning, the weather service forecast snow levels to start Tuesday afternoon around 4,000 feet but rise to somewhere between 6,000 to 6,500 feet.

“Areas north of Interstate 80 will lag behind and will not increase above 6,000 feet until late
Wednesday night,” the weather service wrote in its Tuesday forecast. “By Thursday, all areas will generally be above 7000 feet.”

At the highest elevations, 2 to 5 feet of new snow is expected, according to the weather service.

“It’s going to be a heavy, wet snow,” said Jim Wallmann, a meteorologist with the weather service in Reno.

While rain is expected at lower elevations, meteorologists said the recent accumulation of snow is capable of absorbing most of the rain “given its capacity to hold water at this time.”

The snow …read more

Source:: The Mercury News – Lifestyle


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