Warm winter rains that have curtailed the winter ski season in the Washington Cascades could also mean water shortages this summer.
The reason is that water for summer drinking, irrigation and wildlife needs is usually locked up in deep snow high in the mountains until the spring runoff begins. But in most parts of the Cascades, the January snowpack is at its lowest level in 28 years, said Philip Mote, a research scientist with the Pacific Northwest Climate Impacts Group at the UW and the state climatologist.
Most basins in the Cascades currently have only 20 percent to 30 percent of their normal snowpack, Mote said, even though most have received 70 percent to 80 percent of their normal precipitation. In more than half the areas it is the lowest-snow winter since 1977, and in many others it is the worst since 1981.
“When we’ve had precipitation in the mountains, it’s predominantly been rain,” he said. “Even before the recent warm spell, things were beginning to look grim.”
Even at very high elevations, as high as 6,000 feet, snowpack has not accumulated the way it normally does because temperatures have been warmer than usual. Reservoir managers typically reserve capacity to handle heavy spring runoff and help control flooding, so most of the runoff that has occurred so far has not been captured.
“On average, late January is past the halfway point for snow accumulation. We’re in a huge hole,” Mote said.
Because of the presence of weak El Niño conditions in the tropics, “the climate system is tilted in favor of above-average temperatures and below-average precipitation for the rest of the winter,” said Nate Mantua, a research scientist with the Climate Impacts Group.
Mantua noted that this year’s El Niño is unusual in the way it developed, and that the North Pacific jet stream did not conform to typical El Niño patterns for most of the fall and early winter. In the past there have been a few instances of big recoveries with heavy snow in February and March, but the odds for that happening this year are not great, he said.
Scott Pattee, a Mount Vernon-based water resources specialist with the U.S. Department of Agriculture’s Natural Resources Conservation Service, has been in the field this week examining snowpack at various places in the Cascades, and is pessimistic about such a recovery this year.
“By now we should have had over half our total snowpack, so catching up is going to be pretty tough,” Pattee said. “Some of the lower snow courses have already melted out.”
The situation is particularly dire for fish and for irrigation needs, especially in the Yakima, Wenatchee and Methow river valleys on the east slope of the Cascades, Mote said, with Yakima Valley snowpack at only about 25 percent of average.
“Only 1977 was worse. Although it had a surprise ending, with a snowy March that brought conditions up closer to normal,” he said. “We should not expect a happy ending this time. Odds of that are very slim. Summer streamflows are likely to be very low and the pain will be widespread.”
The conditions, which have sharply curtailed the ski season in the Cascades, are eerily similar to what the Climate Impacts Group has said will become common for the Pacific Northwest in the next 50 to 100 years because of a warming climate.
“As average temperatures rise, so too will the chances of unusually warm weather, which can be the last straw for an already poor snowpack,” Mote said.
“Last week it was well above freezing even at 6,000 feet — and the majority of Cascades snowpack lies between 3,000 and 5,000 feet, where a warm year, or even a warm week, can be devastating,” he said.