Turnagain Pass

Winds are increasing this morning as the next storm approaches. A few more inches of snow are forecasted to fall during the day and there is plenty of soft snow available to transport and to form tender wind slabs in the Alpine. Heavier, wetter snow falling today may make slabs more reactive. In addition, older wind slabs that formed over the weekend may also be triggered on steep leeward slopes. There was one skier triggered slab yesterday on a South facing slope on Lipps. In this avalanche the wind slab was resting on old hard wind crust from the wind event prior to the storm. This combination has been found in steep leeward terrain the past two days. Feel for hollow feeling snow, stiffer snow over softer snow or slab sitting on hard snow and watch for cracks that shoot out from your snowmachine, skis or board. 

Skier triggered slide on Lipps 1.22.17. Photo: Mike Records

There is a significant amount of loose snow from not only Saturday’s storm but the snowfall earlier in the week. Expect sluffs to be triggered on slopes approaching 40 degrees. These are likely to be high volume and run fast and far. Sluff management will be key. In Girdwood Valley these will have more volume due to additional 10″ that fell yesterday. 

A variety of persistant weak layers exist within the snowpack and vary across our region. In most cases these layers have been generally dormant. As more load is added and the slab develops they have the potential to become more reactive. In shallower parts of the area there are developed basal facets and in many locations there is a mid-pack layer of facets from December. At the lower elevations, below 2,000′, a layer of buried surface hoar exists under the last two snowfall events (12-18″ below the surface). Slab avalanches failing on this layer are possible where the snow on top is stiff enough to form a slab. In most locations, the snow is too loose and therefore triggering a slab in unlikely, but it seems the party on Cornbiscuit Saturday may have found one of these lower slopes that did indeed have enough of a slab on this suspected buried surface hoar. The lower terrain in Placer Valley is an area that may have a similar set up. All of these layers are important to remember if we receive a significant load in the next couple of days!!!

Surface hoar layer that was buried on January 13th. Photo from Eddies on January 17th. This layer has been found in a number of locations below 2000′ in the advisory area.