Turnagain Pass

Finding and triggering a slab avalanche that breaks in weak snow 1-2+’ deep in the pack remains a concern. This could be in the form of a lingering wind slab or a much older slab that sits on weak layers in the mid-pack. Although today’s clear skies should reveal a dusting of new snow from yesterday, this is likely only enough to obscure a generally variable and wind affected surface through the region. With a longer sunny day ahead, here are the things to keep in mind:

Lingering wind slabs:  Strong Northwest winds impacted the region last week and due to unusual wind loading patterns, formed hard wind slabs on a variety of aspects. Watch for steep areas harboring stiff snow over softer snow and cracks that shoot out from you. Old wind slabs can be found along ridgelines and in steep rocky terrain, but also mid-slope in cross-loaded gullies. Even a small slab can have high consequences in steep and committing terrain. 

Persistent slabs:  Several weak layers sit in the middle and base of the snowpack and as recent as last Tuesday, skiers triggered a large ‘persistent slab’ in the Summit Lake area. This problem has shown to be more pronounced on the Southern end of Turnagain Pass and Summit Lake where the snowpack is shallower (areas to the North, such as Crow Pass, could also be suspect). Wednesday, during the wind event, numerous large avalanches released naturally near Silvertip Creek and in Summit Lake, most likely due to winds overloading these various weak layers. In short, buried 1-2 feet deep are facets sitting on a crust at the mid-elevations and buried surface hoar at the higher elevations. Whumpfing has been widely reported in the mid elevation band region-wide. If headed out for a long day in the mountains, remember these layers are there and no red flags may be present before a slab releases. 

Solar warming/effects:  Sunshine today along with light winds may allow for enough warming to initiate small wet loose avalanches on steep Southerly aspects. Warming may also cause slabs to be more reactive; something to keep in mind as we choose our late afternoon terrain.  

A wide angle view of Sunburst, Magnum, Cornbiscuit and Lipps – it may be March, but a generally thin snow cover remains

Weak layers in the snowpack at the mid-elevations on the South end of Seattle Ridge

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