Turnagain Pass Avalanche Forecast

The skies cleared just enough yesterday afternoon to get a look at some of the natural avalanche activity that occurred during the storm Wednesday night, just 36 hours or so ago. Several wind slabs released, around a foot thick, that were partially filled back in. The more concerning avalanches however, were several slabs that appeared to have released in deeper buried layers, around 2 feet thick. These were observed on Sunburst, Tincan and Magnum and are pictured below.

Sunburst’s lower north ridge. If you look close you can see the partially filled in ~2 foot crown just off the ridge and extending for several hundred feet. This character of this slab points to failure in a buried weak layer as opposed to simple wind loading.

Magnum’s west face. Despite many sluffs and shallow wind slabs on this face, the spooky avalanche is the one at the top, the pocket that pulled out just under the rocks. This slab is near the slide that was human triggered in weak faceted snow around 3 weeks ago and like Sunburst, is indicative of failure in older weak snow.

This slab, who’s crown is partially filled in by wind, is also suspect for failing in buried weak snow. Located on the north side of Tincan Ridge, the Tincan north chutes, and just over the ridge from Hippy Bowl.

Slab avalanche seen on the Penguin Ridge, SE facing in Girdwood Valley yesterday as well. This slab also has the character of releasing in older weak snow. 1.30.20. Photo: Mike Welch

A typical wind slab, around a foot deep, that released on Tincan’s CRF ridgeline, SW aspect. 

Skies are dawning cloudy this morning, winds are light and temperatures are in the single digits. For those of you headed out and hoping the skies open enough for travel above treeline- BEWARE. There is a lot of uncertainty as to how tenuous the snowpack is right now.

Sitting under all the low-density snow from the last half of January (2-4+ feet of soft powder snow), are weak sugary facets and buried surface hoar. The winds from Wednesday night not only affected the surface snow, but they also tipped the balance just enough to initiate some natural avalanches. Some were in the form of common wind slabs, but what is much more concerning, were the slabs that are suspected to have released in deeper layers in the snowpack. Although the natural avalanche cycle was not widespread, that also means many slopes could still be hanging in the balance, just waiting for a trigger.

Very conservative terrain choices are advised today as the snowpack adjusts. It is just 1.5 days after the end of the natural cycle and although the likelihood of triggering a large slab should be decreasing, patience is key. Things to keep in mind if travel is possible to the higher slopes:

• Don’t forget there is funny business several feet below you…
• No signs of instability may occur before a slope releases
• It could be the 3rd or 10th person on a slope before someone finds a trigger point
• Remote triggering is possible (triggering a slab from below, along the ridge or on the side)
• Avoid heavily wind loaded slopes. These are more likely to release due to the additional weight on the weak layers.

One of many snow stability tests performed on Tincan yesterday. Results were varied and pointed to areas where the buried weak layers were showing signs of reacting and areas they were not.

Video link HERE. 

Lingering wind slabs from the strong winds Wednesday night may still be possible to trigger on steep slopes. These are expected to be around a foot thick and somewhat stubborn. The more concerning issue is if a small wind slab triggers a deeper weak layer and a larger slab avalanche occurs. This can make for a very unmanageable and dangerous situation.

Loose Snow Sluffs:  Expect sluffs on steep slopes in areas that were spared the winds. In the lower elevations, these sluffs could entrain a large amount of older storm snow and be larger than expected.