Turnagain Pass

Triggering a deep slab avalanche 2-4+ feet thick remains a possibility. It has been over two weeks since significant snow fell and almost a week since a large scale Northerly wind event loaded slopes and increased avalanche hazard. Since then, generally quiet weather has occurred yet people are still able to trigger avalanches. Many of these have been remotely triggered from the side or below, such as on Friday when a skier remotely triggered a large avalanche while descending a low angle slope on Raggedtop Mountain in Girdwood Valley.

The problem is old buried weak layers from January. There are facets sitting on a slick melt/freeze crust at the mid elevations and facets mixed with buried surface hoar at the upper elevations. To add to this, strong Northwest winds that ended Thursday caused unusual loading patterns opposite the usual Easterly direction. This means the typical windward slopes with thinner weaker snow may be more loaded and ‘trigger spots’ may be lurking just below the surface in unexpected places. Observers over the last few weeks have found poor structure along scoured ridges and under sastrugi.

The tough thing is, our hard-pack snow surface appears safe and stable but this is not the case. Keep in mind that no obvious clues may be present until the slope releases. It may be the 10th skier or snowmachiner onto a slope that finds a thin part of the snowpack (a trigger point). Triggering a slab remotely from the side or below is possible. Take a moment to visualize the consequences if the slope does slide. 

Remotely triggered avalanche by a skier two days ago in the Girdwood Valley. This was on an Southeasterly aspect around 3,000′ on a lower shoulder of Raggedtop Mtn.

Two snow pits dug on Taylor Pass show one of the weak layers we are concerned about along with the difference in slab height in a short distance.

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Wind Slabs: Easterly winds will be moderate to strong today, yet little snow is available for transport to form fresh wind slabs. However, this is something to be on the lookout for if you head into the hills. Additionally, old hard wind slabs may be lurking on a variety of aspects due to the unusual loading patterns this week. Smooth supportable surfaces where the snow is hollow sounding are suspect, especially if the slope is unsupported in steep rocky terrain. 

Cornices: Cornices are large in places and the sun and above freezing temperatures can make them more unstable. Give cornices plenty of space and limit exposure underneath them.

Taylor Pass on the left photo and Pastoral Glacier on the right. Winds last week stripped the majority of the soft surface snow away. You can see evidence of an old avalanche on the Pastoral Glacier.

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