Turnagain Pass

It was a relatively quiet day in the backcountry yesterday; one day after an eventful Thursday where two large human triggered avalanches occurred with one resulting in a full burial – details on those HERE and HERE. One reason for the quiet day was possibly the low visibility hampering travel too far from treeline and the other possibly, the one we hope, is that people are sticking to lower angle slopes due to the poor snowpack stability. 

Today marks the fourth day since a 3 day storm brought 24-40+” to Turnagain Pass and surrounding zones. Buried under the storm snow is a widespread and intact layer of buried surface hoar that is responsible for the recent avalanche activity. We have been tracking this buried persistent weak layer and it is showing signs of becoming stronger (hence, harder to trigger an avalanche). HOWEVER, we have only been able to access very few areas. These are the same areas folks have been getting into – namely low angle slopes on the Tincan and Sunburst ridges. In fact, our staff deemed the risk too high to investigate the Sunburst avalanche yesterday becuase of the required exposure to steep slope angles. This leaves a lot of unknowns for when skies clear and travel is possible to further reaches of the forecast zone. All signs point to conservative decision making. What we do know is that the buried surface hoar exists to the ridgetops and is covered with a slab that ranges widely: from 4-5′ in the Girdwood Valley to 2-4′ in the Turnagain Pass zone and 1-2′ further south in the Summit Lake area.

For today, continued patience is recommended. Enjoying quality snow conditions can be had by sticking to low angle slopes, avoiding steep rollovers and staying away from the steeper terrain. Click this hyperlink for a definition of a “Persistent Slab” and the Travel Advice associated with it.

The winds kicked up into the 15-20mph range from the North and East yesterday. With plenty of loose snow available for transport, soft wind slabs and drifts formed on leeward aspects. This concern is trumped by the primary concern above, yet is worth noting for two reasons. One, it adds additional load to the slab resting on the buried surface hoar. And two, wind slabs may be found below 2,500′ where triggering a larger slab is less likely.