Summertime temperatures in April accelerated the snow melt in Washington’s mountain ranges, diminishing the outlook for summer water supplies.
Snow pack measurements for most of the state were at or above normal on April 1. But a series of heat waves, including nighttime mountain temperatures that were 20 degrees above normal in some places, has shrunk the remaining snow pack.
Snow accumulations in many basins dwindled to below normal, which means less water for summer stream flows, irrigation, recreation and migrating fish.
“We’re on a steep melt curve,” said Scott Pattee, water supply specialist for the Natural Resources Conservation Service. “If we drain all the water off the mountains with this heat, we might not have adequate flows in the fall.”
The Upper Columbia was among the hardest hit watersheds, with snow accumulations dropping from 134 percent of normal at the beginning of April to about 61 percent of normal on Thursday.
About half of the monitoring sites in the Upper Columbia watershed no longer have snow, Pattee said.
The Spokane River basin, which has lagged below normal for most of the winter, was at 58 percent of average on Wednesday. When temperatures shot into the 80s in Spokane last week, overnight temperatures in the mountains were higher, too. The National Weather Service took an early morning reading of 63 degrees at 4,900 feet in elevation on April 20.
Elsewhere across the state, snow packs are 64 to 85 percent of normal for this time of year. The exception is the Olympic Peninsula and the Lower Yakima River watersheds, which are about 95 percent of normal.
However, the state remains in much better shape compared to last year, when the snow pack in parts of the Cascades dropped into the single digits in April.
Early snow melt and drying of the forests usually coincides with higher numbers of acres burned by wildfires. Following two years of escalating fire activity, the state Department of Natural Resources plans to station additional firefighters, engines and and air tankers in Eastern Washington this summer.
Four wildfire simulation exercises are planned through May to give regional firefighters and local officials the chance to practice before the season starts. Six air tankers will be stationed at airports in Deer Park, Omak and Dallesport in the Columbia River Gorge to provide quick attacks on fires as they are reported.
Wildfire activity across the Northwest and Northern Rockies should return to more normal levels this summer, according to early predictions from the National Interagency Coordination Center.
“Either way, we’ll be prepared,” said Janet Pearce, a DNR spokeswoman.
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