Washington’s snowpack entered April at 131% of normal, according to the Natural Resources Conservation Service, the fourth deepest in the past 30 years and a good omen for irrigators.
The April 1 figure averages snow measurements at sites throughout the state, which can vary greatly. This year, basins all over Washington have healthy snowpacks, typical for a La Nina winter.
Snowpacks started building later in the winter, NRCS water supply specialist Scott Pattee said Thursday. “Once we got through January and into February, it slammed us with La Nina.”
Even though snowpacks are high, 17% of Eastern Washington suffers from a “moderate” or “severe” drought, the U.S Drought Monitor reported Thursday.
Washington State Assistant Climatologist Karin Bumbaco said the region has been getting even less precipitation than usual.
“Looking at March precipitation numbers, they’re very low for some areas of Eastern Washington,” she said. “It’s not an issue for irrigated agriculture because the snowpack is so great.”
The National Weather Service forecasts Columbia River flows at The Dalles this summer will be 91% of normal. The U.S. Bureau of Reclamation reported Wednesday that conditions are promising for Yakima Valley irrigators to have their full water allotments.
Snowpacks typically peak this month and start melting into streams and reservoirs. The National Oceanic and Atmospheric Administration’s Climate Prediction Center forecasts that April, May and June will be cooler than average in the Cascades, another benefit to summer irrigation.
Although a rough measurement, the state’s April 1 snowpack receives ample attention. The snowpack has been above average for eight of the past 10 years.
The snowpack was 137% in 2012 and 115% in 2011, back-to-back La Nina winters. Snowpacks in 2008 and 1999 also surpassed this year’s.
Pattee cautioned against seeing a long-term trend in the April 1 snowpack average. “Trying to use that number as to whether we’re seeing a depleting snowpack or climate change, that you can’t do,” he said.
La Nina winters in Washington are typically cold and wet. The climate phenomenon, in which cool ocean temperatures trigger changes in the atmosphere, typically brings warm and dry winters in the southern U.S. tier.
Drought classified as “exceptional” grips sections of Nevada, Utah, Arizona, New Mexico and Colorado.
The Climate Prediction Center reported Thursday an 80% chance that La Nina will yield to neutral conditions in May.
Looking far ahead, the center projected a 40% chance La Nina will return next winter, compared to a 47% chance that neutral conditions will prevail and a 13% chance an El Nino will form.
Predictions this far out are tentative. El Nino winters are typically warm and dry in Washington. The “snowpack drought” in 2015 occurred during an El Nino.