Turnagain Pass

A short burst of snowfall yesterday morning added a welcome 5-9″ of very low density snow in the Girdwood Valley and 1-4″ at Turnagain Pass. With the chance for a few more inches of light snow today, this will add to the soft surface conditions, but the avalanche concerns will remain deeper in the pack.

The primary concern continues to be a slab (1 – 3+’ deep) sitting on a layer of intact buried surface hoar. Last week this combination (slab + weak layer) was very touchy causing several large human triggered avalanches including a full burial in Turnagain Pass. As this layer has had time to adjust we have noticed it gaining strength and getting harder to trigger in our test pits. Check out this VIDEO from yesterday. Unfortunately, when it does collapse there is a lot of potential to propagate over an entire slope. In other words, the probability of triggering a large avalanche is decreasing, but due to its thickness and potential to propagate, the consequences are high.

In the right type of terrain you might trigger an avalanche or you might not. Many people could ski the same steep slope before someone hits the right trigger spot. It can be nearly impossible to know the exact location of these areas, but a good rule of thumb is to avoid thin snowpack areas, steep convex rollovers and areas near rocks. If you find yourself creeping into steeper terrain be aware of the consequences below you. It can be easy to assume that just because a slope has been skied it is deemed “safe.” 

There is a lot of uncertainty around this avalanche problem. We haven’t received any reports of recent avalanche activity in the last few days. Our observations have been limited to our roadside access on low consequence terrain of Tincan, Sunburst, and Seattle Ridge.  We have only been able to investigate this slab plus weak layer combination on slopes below 35° in Turnagain Pass. We don’t know how reactive this weak layer is south of Sunburst or in elevations higher than 3400’. Girdwood received the highest amount of precipitation from the Dec.14-17^th storm and this slab layer gets gradually thinner as you head south through Turnagain Arm. We know that the Summit Lake area has the shallowest snowpack, and we suspect it could be easier to trigger a persistent slab in this region.