This article comes to us from climate.gov
Few things are more important to California’s water supply than the water content of the mountain snowpack at the start of the state’s warm season. Winter-type storms and snowfall tend to taper off in April and May. Temperatures become warmer and days become longer, causing the snowpack to melt. As spring turns to summer, this melting snow keeps the state’s rivers and streams—and people’s farms, fields, and taps—from running dry.
The snowpack this spring is incredibly small. These photo-like NASA satellite images contrast the snow extent in the Southern Sierra Nevada Range Mountains on May 2, 2015, and May 10, 2003, a year when snow conditions were close to the long-term average. (The large versions of the images show the entire state.) Instead of gleaming white snow tracing ridges and valleys, large areas of bare brown rock appear on the mountain summits in the 2015 image.
The water content of the California snow pack was the focus of the April round of Climate.gov’sClimate Challenge, our social media game where players compete with experts to see who can make the most accurate predictions. The April question was, “What percentage of average snow water equivalent would the Sierra Nevada snowpack contain on May 1, 2015?”
Snow water equivalent is the depth of what that would be produced if the entire snowpack melted at once. The answer to April’s question was an unsettling 3% of normal. Given that California is only one month in to its 6-month dry season—also its fire season—the number is sobering, although not surprising to the region’s water experts.
The experts for the April round of the Climate Challenge were Kevin Werner (Western Regional Climate Services Director), Nina Oakley (Western Regional Climate Center), and Mike Anderson (California State Climatologist). California’s lingering drought loomed large in all their predictions.
The experts’ average guess was that snow water content would be 5.3%—although State Climatologist Mike Anderson guessed the 3% figure exactly. In comparison, the game’s participants’ average guess was a more optimistic 43.98%.
According to the map archive from the U.S. Drought Monitor, drought has been in place in at least some part of California since December 27, 2001. As of May 5, 2015, most of the state was experiencing drought classified as either “exceptional” or “extreme.” Meanwhile, the U.S. Seasonal Drought Outlook for April 16–July 31, 2015, predicted that drought would persist or intensify for nearly all of the state.
California gets most of its precipitation in the fall and winter months, so there is little chance of drought relief this summer, which is bad news for firefighters, endangered salmon and other wildlife, farmers and ranchers, and residents.
Meanwhile, forecasters are keeping an eye on the El Niño forecast for the upcoming winter. Although there is no guarantee, winters with a strong El Niño in the eastern tropical Pacific tend to be wet ones for at least the southern part of California.
Caption by Michon Scott and Rebecca Lindsey. Image by Dan Pisut, based on Terra MODIS satellite data provided by the LANCE-MODIS Rapid Response Project.