Measurements adopted across the Sierra Nevada show that snow packs in California, which typically provide nearly a third of the state’s water supply, are now at 85% of the average for this period.
The latest state data released Friday also shows that the amount of snow in the mountains varies dramatically from region to region. The Northern Sierra has a lot of snow in most areas, while the Central and Southern Sierras are much less than average. This brought Northern California, leaving Southern California dryers, when it brought Southern California heaviest atmospheric river storms.
In addition to these primarily random weather conditions, scientists also see trends related to human-focused climate change. This year’s snowman is significantly smaller at many low-sign sites in the mountains after months of warmer than average.
“It’s a really warm temperature signature,” said Daniel Swain, a climate scientist at UCLA. “There was a lot of rain in the mountains, but it’s more like rain than snow for most of the season.”
Over the central and southern Nevada, average temperatures over the past three months ranged between 2-5 degrees Fahrenheit than the 30-year average. Swain said that snow buildup is less in areas below about 7,000 feet above sea level, despite some high lift locations recording above average snow.
Published in 2023, scientists discovered that snow lines in California mountains are already creeping up high due to rising temperatures, and if they do nothing to slow down the pace of global warming, the mountains could lose more than half of their seasonal snow cover.
Swain said the transition to lower elevation snow was “increasingly seen in warmer climates,” highlighting the need for California to adapt by changing the way water is managed.
The state’s water manager released the latest data as he conducted a monthly snow survey at Phillips Station near Lake South Lake Tahoe.
“We got it in February, so that’s good news,” said Andy Rising, manager of snow surveys and water supply forecasts for the state’s Department of Water Resources. “It’s a decent year, but we certainly want to see these storms there in the next few weeks and get some good snow on the ground for us.”
He spoke after he and others performed manual measurements on the site by driving metal tubes into the snow. They found that its moisture content was 58% of the date average.
The current snowpack level is one of several metrics for measuring California’s water outlook. The other is the amount of water stored in state reservoirs, well above average levels.
Very rainy weather and moderately wet 2024 in 2023, the reservoirs were full, and at the time California water supply was in a relatively good shape heading into spring and summer.
Lake Shasta, the state’s largest reservoir, is located at 78% of its capacity, with the second largest lake Oroville at 84%. Both reservoirs are expected to fully fill spring as they are replenished with rain and run out of the rain.
Other large reservoirs, including New Melones Lake and San Luis Reservoir, are similar to average levels above this period.
“We’ve had two previous rainy years so we’re in good condition,” said Jeffrey Mount, a senior fellow at the Institute of Public Policy at the California Water Policy Center.
Southern California’s Metropolitan Water District supplies 19 million people to six counties, with 3.8 million acre feet of banks depositing its various reservoirs and underground storage facilities. This is about three times the total amount of water the district has supplied each year in the past few years.
“At this point, there is no immediate concern about the city’s water supply,” Swain said.
The snowpack is below average, but has improved after a series of atmospheric river storms. A month ago, Sierra Snowpack.
“This year is another example of California’s traditionally wet seasons that can rapidly sway between wet and dry,” says Reising. He said that after the storm in early February, others dropped several feet of snow on Sierra Nevada, but then “average temperatures and dry conditions have been above two weeks and are already beginning to cut those profits.”
More storms take place in early March, with more rain and snow before the rainy season ends.
Throughout winter and early spring, state water officials use a network of snow sensors combined with manual investigations throughout the Sierra Nevada to measure snow packs. The final survey of the season is scheduled for around April 1st, when snow packs usually peak.
“We don’t have any aggressive snow or rain every day. We may be losing the ground, which is getting worse with warm temperatures,” Reising said. “There’s still about a month left in the traditional snow accumulation season, but we’re quickly running out of time to catch up with an average snowy year like last year.”
This winter, atmospheric river storms followed things like “corridors” in Northern California and southern Oregon, Swain said.
This has created a permanent pattern of unusually wet, snowy weather in Northern California and unusually dry weather in most of Southern California and the Southwest. Swain said current conditions, a cool phase in the tropical Pacific waters cycle, probably contributed to the patterns.
As of Friday, snowmen in the northern Sierra measured an average of 104% of dates, compared to 80% in the central Sierra and 70% in the South Sierra.
“There’s a huge gap from north to south,” Swain said, adding that this pattern of north-south “dipole” is likely to last.
This week, almost 42% of states covering Southern California and the San Joaquin Valley show that they are experiencing at least moderate drought conditions.
The severe drought continues across the basin, another major source of water that Southern California cities and farms rely on. Lake Mead, the river’s largest reservoir, is 35%, and snowmen in the Upper River Basin of Colorado is below average this year.
Over the coming months, Swain said the drought situation is likely to spread and intensify across the lower Colorado River and across Southern California.
However, he said snow and rain elsewhere would likely limit drought progress in central and northern California.
“If we start to enter another drying period and the reservoir levels are still above average, that’s good news,” he said.
