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Before and after: Sierra Nevada snowpack expands steadily over past month

NASA satellite photos show big change due to steady series of recent winter storms

Paiching Wei, graphics director for the San Jose Mercury News. For his Wordpress profile. (Michael Malone/Bay Area News Group)Paul Rogers, environmental writer, San Jose Mercury News, for his Wordpress profile. (Michael Malone/Bay Area News Group)
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What a difference a month makes.

On Jan. 1, the Sierra Nevada snowpack, the source of nearly one-third of California’s water supply, was a meager 28% of its historic average.

RELATED: Bay Area rain map: See where this week’s storms are

October, November and December had brought few storms, leaving ski resorts with many runs closed and water managers around the state beginning to get nervous that California could be heading back into the kind of dry conditions that defined the 2020-22 drought.

But since then, winter has arrived. Multiple atmospheric river storms have sent the Sierra Nevada snowpack back to respectable levels. On Wednesday, it was 74% of the historic average.

Images from NASA satellites show that on Jan. 1, snow was present mostly only at the highest elevations between Lake Tahoe and Sequoia-Kings Canyon National Park in the Southern Sierra.

But by this week, snow was blanketing hundreds of miles at lower elevations, including in the Sierra Foothills, Yosemite National Park, around Mono Lake and other locations.

From New Year’s Day to Wednesday, 11 feet of snow has fallen at the UC Central Sierra Snow Lab at Donner Summit along Highway 80 near Lake Tahoe. That six-week stretch boosted the season total at the lab from 31 inches between Oct. 1 and Jan. 1 to 167 inches now — reaching 79% of normal for that location.

The outlook going forward?

Two significant storm systems are forecast to bring more rain to the Bay Area on Saturday and Sunday, and again Monday and Tuesday. Those storms are expected to deliver up to 2 feet of new snow by Tuesday to Donner Summit, according to the National Weather Service in Sacramento, and up to 4 feet of new snow farther south at Sonora Pass and Ebbetts Pass.

“Maybe Mother nature was a little tired from last year,” said Mike Reitzell, president of Ski California, an industry association. “It took her a while to wake up. But things are looking really good.”

Although the industry got off to a slow start this winter, most ski resorts in the Tahoe area have a snow base of 6 to 10 feet, and all or nearly all of their runs are open now, he said.

“These next storms coming in should really set things up well for the rest of the season,” he said. “The beginning of the year was a little challenging for everybody. Some places didn’t open until after the new year. But since then things have gone a lot better for everyone. The way things are going, we feel good about how the season is going to finish out.”