Turnagain Pass

It has been four days since any known avalanche activity has been seen. The New Year’s storm snow has now settled to around 12 – 20″ at Turnagain Pass and to 20-30″ in the Girdwood Valley. The buried surface hoar that is the culprit for last week’s avalanche activity sits right under the New Year’s snow. This layer is slowly gaining strength and the slab is becoming more stubborn to trigger. However, we are not out of the woods. Snow pit results are still showing this layer to be reactive and to propagate – meaning human triggered slabs are possible if one hits the right spot on the slope. Additionally, there are slopes that avalanched in early December which have a thinner snowpack and harbor another set of facets under the pack. Essentially, we have a thin snowpack with various weak layers.

These problems are relegated to above ~2,000′; due to rain falling up to 2,000-2,300′ on Jan 2nd, which has turned the slab into crusts at these elevations and below. (Remember from your level 1 avalanche course, to have a slab avalanche you must have a slab, not just a weak layer.) Hence, many folks were out enjoying terrain around 2,000′ yesterday without incident, yet most terrain above this, and in the 3,000’+ range, remains untested. Here is a video from 3,000′ yesterday: 

*For those riders and skiers headed out for today’s sun, keep in mind that travel in the upper elevations is where triggering a slab is most likely. This is above 2,500′ where NO crusts exists in the top foot of the snowpack and the snow quality is best. Remotely triggering a slab is possible, several tracks may be on the slope before a slab releases and no signs saying ‘the slope is unstable’ are likely to be present. Larger slopes are more suspect as well and those with rocky features. Safe travel habits are always key, but especially when dealing with persistent and deep persistent slab avalanche problems: exposing one person at a time, having an escape route planned and watching your buddies closely.

The SLAB and WEAK LAYER we are talking about – the “thin grey line”…

In the photo below, the SLAB fails and cracks but doesn’t quite want to fall into the pit on this low angle slope when a snowmachiner side hills just over the pit wall.

Many folks out enjoying terrain in the near 2,000′ elevation zone and below where triggering an avalanche is unlikely. (Photo from Main Bowl/1st Bowl in Seattle Creek drainage)

Old avalanche debris from Jan 2nd – this is at 2,000′ and these lower slopes that were rained on when the avalanche occurred are now frozen and stable. (photo Ray Koleser)

At high elevations above 3,000’, human triggered large and dangerous deep slab avalanches are still possible. Weak sugary snow (basal facets) near the ground is creating a low probability/high consequence avalanche problem that is impossible to outsmart and will take a long time to heal. A big trigger like a snowmachine or a slab avalanche in the upper layers of the snowpack may be enough force to initiate a deep slab avalanche. Likely trigger spots will be in thinner areas of the snowpack that are connected to large, loaded slopes. Cautious route-finding is essential. This includes thinking about the remote trigger potential from below.