At Donner Summit, the snowpack is 47% of average


For those who study the snowpack, April 1st is no joke. It’s record breaking day, when measurements reveal how much water is in the snowpack and how much water California needs to survive the summer.

Historically, scientists have chosen April 1 as the big day for snow measurements because, at the end of winter, that should be the time when the snowpack is thickest. It is a day that divides the water year, between the season when the reservoir of snow across the Sierra Nevada builds up and the season when that snow melts and rushes downstream to lower elevations.

This is not the case this year.


This year, after a record December, snow accumulation peaked months ago and has been flat ever since.

Today, the Sierra Nevada snowpack will be well below average after one of the driest January to March periods on record. Extended months of dry weather and sparse snow were a bizarre turnaround in weather patterns after an atmospheric storm dropped 214 inches of snow in December, nearly 18 feet, atop Donner Summit, breaking a record 50 years of snowfall.

“It’s been a year of extremes, that’s for sure,” said Andrew Schwartz, director and senior researcher at the UC Berkeley Central Sierra Snow Labwhich holds some of the oldest snowfall records in the world.

“We had the deepest December on record, the driest January and February on record, and now our snow is effectively melting about a month before it is [melting] even last year,” Schwartz continued. “And you know, last year was definitely not a good year either.”

The snow-water equivalent is the most critical measurement taken on April 1. It is a number that indicates the amount of water in the snow and helps scientists and water resource managers predict how much water will flow downstream from California’s vast reservoir system.

At the Central Sierra Snow Lab, located 6,894 feet above sea level, the snow-water equivalent was 47% of average, as of March 30.

The average snowfall percentage to date is 96% of average – a much higher number that reflects early winter storms. The snow-water equivalent is much lower because the snowpack has been melting steadily for weeks, much earlier than normal.

“It’s not just a problem for our water supply,” Schwartz said. “But we are looking at, potentially, another catastrophic fire season. That’s the big thing.

The snowpack not only provides Californians with water, it replenishes forests with much-needed moisture to reduce the risk of wildfires. Last year, when the Caldor Fire burned through the Lake Tahoe Basin, fire experts continually expressed concern about how hot the fire was, as there was virtually no moisture in the ground. or in the trees. Anything that caught fire burned quickly and the fire spread rapidly in high winds.

With the snow melting a month earlier than last year, Schwartz is worried about the fire season that could be in store for California this summer.

Earlier this week, Tahoe area experienced a thunderstorm flash on the weather radar. According to The Tahoe Snow Forecaster at Open Snow, Bryan Allegretto, most of the Tahoe Basin received about 1 to 4 inches of snow at higher elevations. And it may be the end of winter.

“It’s quite amazing after such a great start to the season,” Allegretto wrote in his daily weather report this week. “We could add more snowfall to the numbers through May, but we are running out of time at the ski resorts as they start to close this coming weekend over the next two weekends.”

Tahoe and the Sierra have certainly been in dire conditions like this before in the not so distant past. The winter of 2014-15 remains particularly infamous for the little snow that did arrive. A scientific paper, published in the journal Nature Climate Change, analyzed tree-ring records for a 500-year snow history in the Sierra Nevada. The newspaper said low snowfall measurements in April 2015 were unprecedented, the lowest in 500 years. Experts say climate change will continue to reduce spring snowpack in California in the coming years, endangering a crucial part of the state’s water supply.

Due to the large storms in December, measurements arriving today are not expected to set 500-year records. Schwartz said there were still snow banks outside his lab. Some are about 2 or 3 feet tall. However, they melt quickly.

“We still have snow here,” Schwartz said. “But we’re losing him at a pretty fast rate.”

At lower elevations in the Sierra, scientists may even struggle to find snow to measure today. The April 1 snow-water equivalent measurement will take into account readings from locations across the Sierra Nevada.

Thunderstorms could still arrive late in the spring. However, the short term forecast calls for high pressure and warm temperatures through next week.

“A few ski areas will try to hold out until the end of April, but we’ll see how it goes if we see a dry and mild pattern for the next two weeks. My guess is that most if not all will be closed by the end of the month, or Sunday, May 1,” Allegretto said in his post.

Tahoe’s ski resorts are known for their deep snow layers and long ski season. But this year, Allegretto wonders whether East Coast ski resorts in Vermont will stay open later than resorts in the Sierra.

“Unfortunately we have ski resorts like Jay Peak in the northeast that have more snow than some resorts in the Sierra,” Allegretto wrote.



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