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Avalanche Forecast

Archived

Feb 12th, 2019–Feb 13th, 2019

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

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Another 2 feet of snow and wind by the end of Tuesday will maintain dangerous conditions. Use caution on slopes over 35 degrees where the new snow slides easily. The most dangerous slopes will be near above treeline where the wind will drift new snow and where older stiff slabs are buried on sunny slopes.

Discussion

Snow and Avalanche Discussion

Avoid southeast through southwest slopes where you find stiff slabs below the snow surface.

The new snow has hidden older slabs, formed on February 9th, by north and east wind. This wind event created unusual wind loading patterns. On southeast through southwest aspect near and above treeline, these stiff slabs sit on a layer of weak sugary facets with an underlying crust. This was the snowpack structure at the site of a remotely triggered avalanche on Sunday (see photo). Use your probe to feel for very stiff snow at least 2 feet below the snow surface.

We received a report of a large, remotely triggered wind slab avalanche near Ptarmigan Ridge in the Mt Baker backcountry Sunday. This avalanche was approximately 2 feet deep and failed on a layer of sugary facets. Unusual avalanches like this should cause us to take notice. Avalanche Details: 2/10/19: SW aspect, 5200 ft. 45-degree slope.

Photo: Remotely triggered wind slab from Sunday. 

Snowpack Discussion

New Regional Synopsis Coming Soon

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.