North Cascade 2019 Winter Accumulation Assessment

For North Cascade glaciers the accumulation season provides a layer of snow that must last through the melt season. A thin layer sets the glaciers up for a mass balance loss, much like a bear with a limited fat layer would lose more mass than ideal during hibernation.

The 2019 winter season in the North Cascade Range, Washington has been unusual. On April 1, the retained snow-water equivalent in snowpack across the range at the six long SNOTEL sites is 0.72 meters, which is ~70 percent of average. This is the fifth lowest since 1984. The unusual part is that freezing levels were well above normal in January, in the 95 percentile at 1,532 m, then were the lowest level, 372 m of any February since the freezing level record began in 1948. March returned to above normal freezing levels.

April 1 winter accumulation at the longer term North Cascade SNOTEL stations (Fish Lake, Lyman Lake, Park Creek, Rainy Pass, Stampede Pass, and Stevens Pass).

As is typical, periods of cold weather in the regions are associated with reduced snowfall in the mountains and more snowfall at low elevations. In the Seattle metropolitan area February was the snowiest month in 50 years, 0.51 m of snow fell, but in the North Cascades snowfall in the month was well below average. From Feb. 1 to April 1, snowpack SWE at Lyman Lake, the SNOTEL site closest to a North Cascade glacier, usually increases from 0.99 m to 1.47 m. This year, SWE increased from 0.83 m to 1.01 m during this period.

The Mount Baker ski area snow measurement site has the world record for most snowfall in a season: 1,140 inches (28.96 m) during the 1998-99 snow season. The average snowfall is 633 inches (16.07 m) with snowfall this year, as of April 15, at 533 inches (13.53 m). Below is a Landsat image from April 15, 2019 indicating the snowline at ~1000 m in the Nooksack River Valley and 900-1000 m in the Baker Lake valley.

Freezing levels at Mount Baker, WA from the North American Freezing Level Tracker. February was the lowest mean freezing level since 1948.

This year, for the 36th consecutive year, the North Cascade Glacier Climate Project will be in the field measuring North Cascade glaciers. The early signs point towards a seventh consecutive negative balance year.

Mount Baker cloaked in winter snow in an April 15, 2019 Landsat image. MB=Mount Baker, MS=Mount Shuksan, NR=Nooksack River

This article was originally published on the blog From a Glacier’s Perspective.

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