Turnagain Pass

• On Notch Peak in Girdwood a group reportedly remote triggered a small avalanche which appears to have failed at the interface between the new storm snow from this week and the old snow surface.

Remote triggered avalanche from Notch Peak in Girdwood 11.24.21. Photo courtsy of Heather Johnson

Happy Thanksgiving!!!

Turnagain Pass has received 15-30” of low density snow since early Tuesday morning with strong easterly winds that ended early yesterday morning. This new snow fell on a variety of existing weak layers and is not bonding well to the old snow surface. The storm snow that has been blown into wind slabs at higher elevations will likely be easier to trigger than in wind sheltered areas. Cautious route finding and sticking to lower angle terrain below 35° will be the best way to avoid these sensitive storm slabs. Watch for shooting cracks and collapsing to identify locations where the storm snow is sensitive to triggering. It is also important to be aware of steeper slopes above you because avalanches could be triggered remotely from low angle terrain below, to the sides, or above steeper terrain.

Over the past couple of days the new snow has not been acting like a slab in areas where people have travelled because it is so light and unconsoildated. As the new snow settles into a more cohensice layer we are concerned it will start behaving more like a slab and conditions could become more reactive. In Summit Lake the snow depth from the latest storm is only 4-6″ and observations from the area have highlighted lingerly hard wind slabs (details).

Our current list of potential weak layers includes two layers of buried surface hoar as well as multiple layers of faceted snow. On Tincan yesterday these layers were buried between 20-30” (with an additional ~5″ overnight) deep and were showing the ability to propagate a slab in our stability tests. Any of these layers has the potential to cause a larger avalanche than expected due to wider propagation. This instability is looking like it may persist longer than normal because of the types of weak layers we are dealing with. 

Snowpack summary from Tincan on 11.24.21

The distribution of surface hoar and faceted weak layers in our advisory area is variable. Digging a snowpit or hand pit is the best way to determine what weak layers exist in the area you are travelling. An extended column test is a great tool to determine the most concerning weak layers and show whether the new snow will propagate. However, one snowpit only represents the snowpack structure in a single area so choose a location that is representative of the slope you intend to travel on and continue to evaluate the snowpack structure with hand pits in multiple locations.

Loose Snow Avalanches: In areas where the new snow is too loose to act like a slab sluffs (dry loose) avalanches are likely in steeper terrain.

Glide activity seems to have slowed down in the past few days, but that doesn’t mean the hazard is gone. Glide avalanches are hard to predict, and they involve the entire snowpack so they are large and very dangerous. Be on the lookout for glide cracks, and limit the time you spend traveling below them.