Snowpack in the Sierra Nevada Is Growing—And It Could Lead to an Avalanche

The winter storm that has caused extreme windy and rainy weather across the state of California has also brought much more snow than normal on the Sierra Nevada mountain range.

"As of today, California's snowpack is at 215 percent of average [for this time of year] with a lot of the snow falling in the southern Sierra Nevada, where it has been needed the most," Andrew Schwartz, the lead scientist and manager at the Central Sierra Snow Laboratory, UC Berkeley, told Newsweek.

"With substantial storms predicted over the next 7-10 days, we could see this number increase significantly but it's hard to tell just how much it would go up."

The Sierra Nevada mountains, which are situated primarily in California, stretch 400 miles from north to south, between the Central Valley of California and the Great Basin. The range includes some of California's most famous sights, including El Capitan in Yosemite National Park, and the giant trees of Sequoia National Park.

Since the atmospheric river storms have hit the state, large amounts of snow have kept falling in the mountains while deluges of rain have battered the lower elevations.

"We have 9.3 [inches] (23.5 cm) be of new #snow in the last 24 hours. The lab is at 172% of average precipitation and 178% of average snow water equivalent," tweeted the UC Berkeley Central Sierra Snow Lab.

"Snowfall rates should increase this morning and we are looking at another 18-36 [inches] of accumulation in the next day."

On January 8, the lab also tweeted that 8.5 inches had fallen in the previous 24 hours, and on January 6, 20.3 inches in the previous 48 hours.

This snowfall has caused chaos on the roads in the area, with drivers on the I-80 in Donner Pass becoming stuck or sliding around on the snowy and icy highway.

The Sierra Nevada snowpack usually peaks around April 1. Currently, the snow is at 76 percent of that peak, California Department of Water Resources (DWR) data shows.

Sierra Nevada snowmelt supplies about 30 percent of California's water requirements throughout the year, meaning that this larger snowpack could help with California's drought in the coming months, by replenishing reservoirs and groundwater levels. The rainfall around the state is also helping alleviate California's drought in small areas.

"Big snow totals are always welcome, but we still have a long way to go before the critical April 1 total," said DWR's Snow Surveys and Water Supply forecasting unit manager Sean de Guzman in a January 3 report. "It's always great to be above average this early in the season, but we must be resilient and remember what happened last year. If January through March of 2023 turn out to be similar to last year, we would still end the water year in severe drought with only half of an average year's snowpack."

The increasing snowpack may pose some risk, as it could create flooding when it melts, or even cause an avalanche that could damage infrastructure.

"As far as snowpack water storage, there isn't really too much risk with an above average snowpack unless we get a sudden melt event, which can cause flooding," Schwartz said.

"However, we do have some risks associated with increasingly snowy conditions, such as increased avalanche risk, strain on structures and equipment, and problems with travel during the storms. One of the largest issues that we see in above average years around the Donner Summit area is propane leaks that develop from tanks buried under the heavy snow. It has resulted in explosions in the past."

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Correction, 1/13/23, 8:30 a.m. ET: This article was updated to remove an erroneous reference to giant redwood trees in Sequoia National Park.