These are boom times for Washington’s mountain snowpack, a vast frozen reservoir vital to sustaining many of the state’s rivers and streams. As of Wednesday, the cold, wet weather of December and early January has pushed the statewide snowpack to 122% of the norm measured during a three-decade period ending in 2020.
This is the second year in a row that the early winter snowpack looks promising for providing strong water flows into the summer months. Last year, however, an unusually hot, dry spring caused an extraordinarily rapid melt and gave way to record heat in June and a summer drought in parched forests.
By midcentury, climate-change models predict that rising global temperatures, driven by greenhouse-gas accumulation in the atmosphere, will result in the annual snowmelt shifting three to four weeks earlier than in the 20th century. And, summer water flows are projected to be substantially lower, according to the National Climate Assessment.
But Scott Pattee, water-supply specialist for the Natural Resources Conservation Service, does not expect a rerun of 2021 in the upcoming spring, which he termed an outlier and an oddity compared with recent decades of spring snowmelt and rainfall patterns.
“Statewide, we are sitting fine. I don’t think we are [going to be] having water concerns,” Pattee said.
Some areas of Washington have streams that don’t get a big boost from the snowpack. But it is vital to many farmers east of the Cascades who depend on runoff to keep water in their canals, which they tap to keep their orchards and fields green.
The snowpack, in a long, cool spring-summer melt, also helps keep the flows up — and cool — in many of the state’s salmon streams, and also supports wildlife and provides moisture for forest growth.
This year’s snowpack is predicted to climb a lot higher during the next 10 days when more storms are expected to hit the region and dump many more feet of snow in the higher mountain elevations.
This represents a dramatic turnaround from November. That month, higher temperatures caused much of the precipitation to fall as rain, which caused severe flooding in parts of northwest Washington and British Columbia. By the month’s end, the snowpack was only at 50% of normal.
“You tell yourself … keep your anxiety in check, said Jeff Marti, who works in the water-resources program of the state Department of Ecology. “But it was low to the point where you start wondering when is winter going to start.
As of Jan. 5, the Lower Columbia basin snowpack, at 136%, was the most ahead of the long-term norm. The Central Puget Sound basin ranked second at 134%. The upper Yakima basin, at 98%, was trailing slightly behind the long-term norm.
To the south, Oregon, at 153%, is a lot further above the norm than Washington. And in California, which has been slammed by massive storms in the Sierra Nevada, the snowpack on Jan. 5 was at 193% — nearly double the norm.
In Washington, the lower temperatures of recent weeks have caused a lot of snow to pile up in lower elevations. These areas also pose a greater flood risk, as warmer weather can result in storms that send both melting snow and rain rushing down slopes.
On Friday, in southwest Washington, the Chehalis River near Grand Mound is forecast to reach a major flood stage. The Skookumchuck, near Bucoda, and the Newaukum River, near Chehalis, are expected to reach moderate flood stages.