Mar 31, 2023 - Science

California snowpack reaches all-time high after 17 atmospheric rivers

 In an aerial view, a church stands in the Sierra Nevada mountains, after yet another storm system brought heavy snowfall further raising the snowpack, on March 29, 2023 in Mammoth Lakes, California.

An aerial view of Mammoth Lakes, California, in the Sierra Nevada mountains after another storm brought heavy snowfall on Wednesday. Photo: Mario Tama/Getty Images

California's snowpack is at record-high levels following a relentless series of atmospheric rivers — and forecasters warn another winter storm is due to hit the Golden State this weekend.

The big picture: The latest bomb cyclone associated with an atmospheric river that dumped more heavy snow across the Sierra Nevada this week helped break the record 1982-1983 season in terms of water content on Thursday, per the California Department of Water Resources.

  • Seventeen atmospheric rivers have struck California since December, according to Scripps Institution of Oceanography.
  • The onslaught of storms means that more than half of the state is no longer considered to be in drought — with 45% of California now estimated to be "abnormally dry," data from the Drought Monitor published Thursday shows.
A screenshot of a tweet from Scripps Institution of Oceanography saying "We have #AtmosphericRivers to thank for all this recent rain! 🌧️ The team from  @CW3E_Scripps  says we are at 31 atmospheric river events so far this water year (11 weak, 13 moderate, 6 strong, 1 extreme)."
Photo: Scripps Institution of Oceanography Twitter

By the numbers: The statewide snowpack was sitting at 236% of the peak normal as of Thursday.

  • In the Sierra, it's 298% of normal in the region's south, 233% in the center and 191% in the north, where a record set in the 1982-83 season still stands.
  • Mammoth Mountain confirmed it recorded its snowiest season following this week's storm, with 702 inches falling in total at its main lodge and the U.C. Berkeley Central Sierra Snow Lab reported its second-highest seasonal total — 713.8" since Oct. 1.

For the record: Atmospheric rivers are long, narrow highways of moisture that can travel thousands of miles.

Between the lines: Climate change is adding even more moisture to atmospheric rivers, enabling them to dump higher rain and snow totals, per Axios' Andrew Freedman.

What's next: Another winter storm threatens to bring more heavy snowfall and strong winds to the Sierra Nevada over Sunday night, the National Weather Service's Reno office warns in a forecast discussion.

A screenshot of a UC Berkeley Central Sierra Snow Lab tweet saying, "What a difference a wet month makes to drought! The 1.2" (3 cm) of #snow that fell over the last 24 hours will contribute to easing drought conditions in California.  The snow season hasn't ended yet and we have another storm expected this Sunday into Monday. "
Photo: U.C. Berkeley Central Sierra Snow Lab/Twitter

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