Record hot, dry March leaves no measurable snow for April survey

The Department of Water Resources (DWR) on Wednesday conducted the critical April snow survey at Phillips Station and found no measurable snow, a stark indicator of how record-hot March temperatures and high‑elevation rain have erased the Sierra Nevada snowpack months ahead of schedule. The combination of warm storms and unusually hot temperatures rapidly melted what remained of this year's already-sparse snowpack. Statewide, the snowpack is now just 18 percent of average for this date, according to the automated snow sensor network. Wednesday's results are the second-lowest April measurement on record for Phillips Station, largely because there was still snow on the ground. By contrast, the lowest April measurement occurred in 2015, when no snow was present at the site. DWR and its partners in the California Cooperative Snow Surveys Program are completing additional surveys across the Sierra Nevada. The April measurement is a critical marker for water managers across the state, as it is typically when the snowpack reaches its maximum volume and begins to melt. However, this year's extremely hot and dry conditions throughout March, along with a warm atmospheric river system in late February, initiated snowmelt several weeks ahead of schedule. According to automated sensors across the Sierra Nevada, this year's statewide snowpack likely reached its peak on or near Feb. 24. "It feels like we skipped spring this year and dropped straight into a summer heatwave," said DWR Director Karla Nemeth. "What should be gradual snowmelt happened suddenly weeks ago. To me, this is another reminder that aging water systems need to be retrofit for more volatile precipitation patterns. We're seeing fewer, warmer storms and shorter wet seasons. Future water supplies will depend upon our ability to capture water when it's available and manage it more efficiently." DWR's water supply forecasts use data from the April 1 snowpack to calculate how much snowmelt runoff will eventually make its way into California's rivers and reservoirs. This information is critical for reservoir managers, who must balance flood control and water supply goals through the winter and depend on snowmelt to slowly refill reservoirs as demand increases during the dry season. Given the unprecedented heatwave across the West in March, DWR and its partners expanded monitoring efforts to better track this year's rapid snowmelt, including 100 additional mid-month snow surveys across 18 critical watersheds. The California Cooperative Snow Surveys Program has also been working closely with partner agencies to monitor the snowmelt and ensure water managers have the information they need to make informed water management decisions. DWR has focused efforts over the past five years to understand and track how snowpack accumulation and melt translates into water supply, which has aided efforts to forecast runoff in new extreme climate conditions. New snow hydrology modeling in key watersheds gives DWR better insights into the changing physical state of the snowpack. Expanding data collection efforts with Airborne Snow Observatories Inc. and academic research partners, including UC Berkeley's Central Sierra Snow Lab, now also allow DWR to consider factors like changes in soil moisture and snowpack temperature in its runoff forecasts. "What makes this year stand out is the disconnect between precipitation and snowpack," said Andy Reising, manager of DWR's Snow Surveys and Water Supply Forecasting Unit. "We received near-average precipitation in many parts of the state, but much of it fell as rain instead of snow. That led to one of the lowest April snowpacks on record and one of the earliest peaks we've seen in decades — conditions that make forecasting runoff more complex." Although additional snow is forecast to arrive in the coming days, it is not likely to make up for the rapid snowmelt and hot, dry March. In the Northern Sierra Nevada, where the state's largest water supply reservoirs are located, the snowpack is just 6 percent of average. Measuring California's snowpack is a key component of water management. On average, California's snowpack supplies about 30 percent of California's water needs. Its natural ability to store water is why California's snowpack is often referred to as California's "frozen reservoir." The data and measurements collected from DWR and its partners with the California Cooperative Snow Surveys Program help inform the water supply and snowmelt runoff forecasts, known as the Bulletin 120, that help water managers plan for how much water will eventually reach state reservoirs in the spring and summer. This information is also a key piece in calculating State Water Project allocation updates each month. DWR conducts four or five snow surveys at Phillips Station each winter near the first of each month, January through April and, if necessary, May. For California's current hydrological conditions, visit https://cww.water.ca.gov