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RegisterMar 15th, 2020–Mar 16th, 2020
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Dangerous avalanche conditions continue on Monday with a major warming trend after recent snow and wind. Expect that natural wet avalanches could be big enough to kill you on steep, sun-exposed slopes You can trigger slab avalanches on open, wind loaded slopes 35 degrees and steeper at most elevations.
On Sunday, observers reported a few small loose avalanches on steep sunny slopes. A storm starting on the 13th delivered almost 2 feet of snow to the Wenatchee Mountains with about half those accumulations closer to the Cascade crest. Saturday was a very active day with reports of natural and triggered slab avalanches as well as widespread cracking and collapsing at most elevations. Many observations came from the Wenatchee Mountains near Blewett Pass, while a notably large wind slab avalanche with a crown up to 6 feet deep was reported in the Napeequa drainage. Mission Ridge reported extensive avalanches with control work including crowns up to 300 feet wide. Most reported avalanches occurred between 5,200-6,500ft on W-N, leeward aspects and involved wind affected storm snow. Many avalanches were reported to have run on a mid-storm interface or small facets just an inch or two above a crust buried by the storm on the 13th.
The unique character of this storm focused on the Wenatchee Mountains. Prior to this storm, snow cover was very shallow there. Stumps, logs, and rocks may be shallowly buried under the new snow. Use caution not to run into these obstacles. In areas closer to the Cascade Crest like the Teanaway, Icicle, and Entiat drainages, as well as the area around Holden Village, the avalanche problems will be similar but some of those locations received less recent snow.
A skier triggered avalanche, size D1, near Diamond Head, Blewett Pass, NW, 5200ft. 3/14/2020. Photo: Adam Butterfield
March 12, 2020 (The regional synopsis is updated every Thursday @ 6 pm)
From March 6th to the 12th the Pacific Northwest experienced a few small storms and a few notable days for people and avalanches. Light to moderate snow accumulated slowly over a period of a few days, and avalanche danger increased from Low to Moderate over the weekend of March 8th. The exception was the West North zone, which won the snowfall competition this week. 18-24” of new snow was observed in the Mount Baker area on the 6th, and 10” of new snow on the 11th. Avalanche danger reached Considerable there for storm slab, wind slab, and loose wet avalanche problems.
People, complicated avalanche terrain, and lots of avalanches. Bagley Lakes Basin, West North zone. Photo by Nathan Resick, March 8, 2020.
Loose dry slides initiated by skiers in big terrain. No one was caught or carried. East Central zone. March 8, 2020. Matt Primomo photo.
The snow fell with minimal wind, and accumulated slowly over firm suncrusts or wind stiffened surfaces. Thicker cloud cover inhibited the sun in areas where 4” to 12” of snow accumulated over the course of a few days. Cold overnight temperatures allowed the low density snow to weaken. By the 8th, the clouds broke up enough to allow strong radiation to change snow surfaces. When the sun finally did hit the snow, it quickly caused loose avalanches in steep terrain.
An active weekend for people and avalanches:
Many areas experienced some form of loose avalanche activity from March 6th to 9th. Sunday, March 8th was the day that recorded the most widespread avalanche activity across the region. The size of these avalanches were directly related to the amount of new snow that had recently accumulated in that area, and the size of the terrain.
West North zone on March 8, and West South zone on March 8th. Uphill and downhill tracks got covered by debris. Photos by Zack McGill and Dallas Glass.
We as a community can look back at, and learn from these few days. Numerous human triggered slides occurred, some were slabs but the majority were loose. A number of catch and carries were observed, and many more likely went undocumented. Luckily, no injuries or burials were reported. Observers across the region reported lots of instances where previous tracks got hit with debris, either from human triggered or natural avalanches.
As the days get longer and folks begin to step into the alpine zone and bigger terrain more frequently, it is important to keep a humble attitude. Continuously evaluate route selection with potential for loose wet and cornice falls in mind. Check the mountain weather and avalanche forecasts for the most up to date info. Enjoy the backcountry, be safe, and let us know what you see out there!
-MP
Solo snowboarder aired into this slope, and went for a ride but was not buried or injured. Slide took out the corner of a skin track. Bagley Lakes Basin, March 8, 2020, Zack McGill photo.
Wind slab triggered by a skier at 7,500ft next to the popular route on Mt St Helens. The skier wasn’t caught or carried. Andy Goodwin photo, March 8, 2020.