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Warming causes worries for Washington snowpack

Warm temperatures are forecast for the rest of February which could jeopardize Washington’s mountain snowpack needed for irrigation.
Dan Wheat

Capital Press

Published on February 6, 2018 9:11AM

Last changed on February 8, 2018 4:17PM

Lowland snow is gone looking up the Wenatchee River from the Columbia River, Feb. 5. A warm February is forecast heightening snowpack concerns.

Dan Wheat/Capital Press

Lowland snow is gone looking up the Wenatchee River from the Columbia River, Feb. 5. A warm February is forecast heightening snowpack concerns.

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YAKIMA, Wash. — Lowland snow on the east slopes of the Cascade Mountains is far less this winter than last and a warm February could threaten snowpack needed for summer irrigation.

Statewide snowpack was 100 percent of normal on Feb. 5 and water storage in Yakima Basin reservoirs was 131 percent of average, according to the Natural Resources Conservation Service and U.S. Bureau of Reclamation.

It was 68 degrees Feb. 4 in Yakima and 57 in Wenatchee, according to the National Weather Service.

“We’ve had three to four days of considerably above normal temperatures and rain which does not bode well for building mountain snowpack as we should be doing,” said Scott Pattee, NRCS water supply specialist.

“It’s all a function of La Nina. Warm and wet,” he said.

Snow depth shrunk several inches in a few days but not water content and soil moisture is good, Pattee said.

Snowstorms could rebuild snowpack or even just cooler temperatures could maintain existing snowpack, but the February outlook is for above normal temperatures and equal chances of precipitation, he said.

March and April are expected to be below normal in temperature and above normal in precipitation, he said.

“If we go through February with higher than normal temperatures, that could start to hurt if we’re not getting snow, just rain. This time of year, we should be collecting snow in the mountains every day and we’re getting rain,” Pattee said.

Chris Lynch, U.S. Bureau of Reclamation hydrologist overseeing the Yakima Basin’s five mountain reservoirs, said the water situation looks good but that he doesn’t want to lose ground and never likes to see mountain snow melting in February.

“Snowpack isn’t bad right now but we don’t have a lot of snow-building weather in our forecast,” he said. “December was dry in the middle and came back strong at the end. Historically, the basin builds snowpack through mid-April.”

The five reservoirs, serving 464,000 acres of Yakima Basin farmland, were at 66 percent of their 1,065,400-acre-feet capacity on Feb. 5. Precipitation at the reservoirs for the first five days of February was 8.65 inches and water year-to-date precipitation (Oct. 1 through Feb. 4) was 170 inches or 122 percent of average.

Preliminary April through September streamflow forecasts call for normal to slightly above normal flows for the upper and central Columbia River regions, Pattee said.

“Some of the best snow in the state is in the upper Columbia and into Canada,” he said.

Snow water equivalent snowpack in the Spokane basin was 106 percent of normal on Feb. 5. The upper Columbia (Okanogan and Methow rivers) was 131 percent. The central Columbia (Chelan, Entiat and Wenatchee) was 106, the upper Yakima was 92 and the lower Yakima 95. Walla Walla was 76, the lower Snake River was 103, the lower Columbia was 84, south Puget Sound (from Cascade crest to lowlands) was 80, central Puget Sound 90, north Puget Sound 116 and the Olympics 126.

Snow is sparse below 4,000 feet in the foothills west of Wenatchee. Lowland snow levels and lack of snow are normal for this time of year but noticeable compared with a year ago which was above normal, Pattee said.


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