Sierra Nevada Mountains

Fresh snow coats peaks in the Sierra Nevada on July 9. The strange weather is thought to be related to El Nino. (Bartshe Miller / Mono Lake Committee)

By Hailey Branson-Potts and Rong-Gong Lin II
July 23, 2015

It’s the middle of the summer, but it felt a bit like winter in the Sierra this week as a storm dumped four inches of hail on Interstate 80 around Donner Summit.

There was so much pea-sized ice that the California Highway Patrol on Tuesday halted traffic and called out snowplows — known as the “Sierra Snowfighters” — for help.

“It looked just like snow, a blanket of snow across all the lanes,” said California Department of Transportation snowplower John Wheeler. “It was really weird.”

The hail storm was just the latest strange weather to hit the Sierra Nevada, influenced by the weather-changing phenomenon El Niño. For months, climate scientists have said El Niño is likely to bring more rain to Southern California this winter.

But here’s the big question in a state enduring four years of severe drought: How far north will El Niño’s influence roam?

The El Niño hitting the mountains of the north is critical because California’s vast waterworks rely on rain and snow from the Sierra to supply farms and cities. By contrast, much of the rain that falls in Southern California ends up in the ocean.

Experts are becoming more optimistic about El Niño’s northern reach.

Only three months ago, all of California had an equal chance of a wet or a dry winter. But in May, the scales began to turn in favor of a wet winter.

By June, the official forecast by the National Oceanic and Atmospheric Administration predicted that both Southern California and the San Joaquin Valley would be in a region where odds favored wet conditions. Last week, the line moved north again, and San Francisco was included.

Still, the area north of San Francisco, where California’s largest reservoirs — Shasta Lake and Lake Oroville — sit, has an equal chance of a dry or wet winter.

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