Turnagain Pass

• Girdwood – A large avalanche was triggered using explosives during avalanche mitigation in the cat ski area on the Sunnyside of Notch Peak yesterday. The avalanche ranged from 2-8′ deep at the crown and may have stepped down onto some kind of buried weak layer but there was no obvious persistent weak layer at the bed surface.

Another day of light winds and warm temperatures is on tap today, with visibility potentially the biggest challenge for mountain travel again. Human triggered avalanches are possible in areas with lingering wind slabs up to 3′ deep, but we expect they will be stubborn to trigger now that the snowpack has had some extra time to adjust to the new snow and wind loading from Thursday and Friday. The most likely place to find a lingering wind slab that could produce an avalanche is along upper elevation ridgelines, cross loaded gullies, and convex rollovers. Temperatures got pretty warm yesterday, with freezing level creeping up to about 2000′ which created some moist snow on the surface that should add strength to the upper snowpack as it freezes.

Wet Loose: The warm temperatures yesterday afternoon created prime conditions for roller balls which is a sign that wet loose avalanches are likely in steeper terrain. If the temperatures rise again this afternoon then expect wet snow at the surface to be creating roller balls and wet loose avalanches again. In general these are not large enough to bury a person, but can be heavier than expected and push you around.

Glide: Another fresh glide crack was observed above the Seattle Ridge up track yesterday. These are a familiar sight this year, but it is important to remember that they can release randomly and cause very large and destructive avalanches. It is best to minimize time spent underneath them.

Shooting crack on a wind loaded slope at upper elevations on Tincan yesterday. Photo from Andy Moderow 2.26.22

Fresh glide crack above Seattle Creek up track that appeared yesterday. Photo from Andy Moderow 2.26.22

A few larger avalanches were observed in Lynx Creek and Goldpan yesterday that likely released during the strong winds and snowfall on Friday. These had wider propagation than most of the activity we observed during the last storm and may have stepped down to an older layer but were probably not deep enough to have involved the November facets that we are most concerned about. An explosive triggered avalanche on the Sunnyside of Notch Peak in Girdwood had an alarming crown depth ranging from 2-8′ deep, but we are not sure whether there was a persistent weak layer involved or if it was just a very deep wind loaded pocket.

The snowpack has had some time to adjust to the new load, which will decrease the likelihood of triggering an avalanche on a deeper weak layer. In general, we recommend carefully evaluating the snowpack for persistent weak layers if you are travelling in avalanche terrain in an area with a shallow snowpack (less than ~6′ deep), such as Crow Creek, Lynx Creek, or Silvertip Creek. We have observed widespread weak snowpack structure in these shallow areas and the potential exists for large and wide propagating avalanches. Due to the depth of the weak layers and strength of the upper snowpack the chances are pretty low for a person to trigger an avalanche on a deeper weak layer without some kind of larger trigger, like a cornice fall or another avalanche. However, the consequences of triggering an avalanche on one of these layers could be very high so we are continuing to monitor and evaluate the distribution of these weak layers.

Larger avalanche in Goldpan area that appeared to have stepped down into an older layer. Photo 2.26.22

Another larger avalanche from Lynx Creek that produced a lot of debris, but may have just been a series of large and well connected wind slabs. Photo 2.26.22