Turnagain Pass

Yesterday there was a very large snowmachine triggered avalanche in Lynx Creek. Both riders were on the slope when it slid but were not buried. The slope that avalanched was on an aspect loaded by the outflow winds and potentially stepped down to the January facets.

Lynx snowmachine triggered avalanche observed from above. 3.5.20. Photo: Paul Forward

Lynx snowmachine triggered avalanche. Thanks to the party involved for sharing images and information. 3.5.20.

The outflow winds (west/northwest) continued yesterday, finally easing off in the late afternoon. Today determining whether or not the slope you are traveling on was wind affected will be the key to avoiding most of the current avalanche issues. Wind slabs remain possible in wind loaded terrain. The snowmachine triggered avalanche in Lynx Creek, that is highlighted above in recent avalanches, occurred on a slope that was being actively loaded yesterday and the day before. This looks to have potentially been initiated failing below the wind loaded layer and then stepping down deeper to older buried weak snow (more below in Avalanche Problem 2). Another part of the equation is that underneath the wind affected snow there could be buried surface hoar making the wind slabs easier to trigger and possibly propagate further above or to the side than expected. There were a couple small skier triggered avalanches in upper Girdwood Valley yesterday including one remote trigger that were believed to have failed on this layer around a foot deep. Be on the lookout for stiff snow over softer snow, shooting cracks and drifting patterns near ridgelines and in gullies where the snow looks pillowed or fat. Much of the core Turnagain Pass area seems to have been spared but as soon as you get to either end of the pass the wind effect is fairly obvious. Summit Lake, which is out of the forecast area, was harder hit by the outflow winds and there was a natural wind initiated avalanche cycle over the past couple days.

Cornices:  Avoid travel on or underneath cornices.

Loose snow avalanches:  In areas that were protected from the wind, sluffs are possible in steep terrain.

Sun effect:  With calm winds and temperatures increasing today look for signs of sun effect on steep solar aspects: moist surface snow, small roller balls or loose snow avalanches in protected spots, especially below rocky areas.  Slopes that are also wind loaded may be more prone to triggering if they heat up enough.

Wind transport in the early afternoon on the northeast corner of Pyramid Peak yesterday. 3.5.20

Wind triggered avalanche that occurred yesterday on Summit Peak in Summit Lake yesterday. Note the wind effect on the slopes and scoured ridges. 3.5.20. 

The avalanche that occurred in Lynx Creek looks to have possibly stepped down to the older faceted January snow. This hasn’t been confirmed. However, it’s not a bad idea to keep this on your radar as you choose terrain today. Triggering an avalanche in the upper snowpack could initiate an avalanche that breaks down lower. As we keep saying those buried facets are a lingering concern, a nagging what if.  These layers are buried between 3-6 feet deep. Overall as time has gone by, the likelihood of triggering has been decreasing but today has a couple factors that could swing that the other way.  Terrain that was just wind loaded could be a bit more stressed and prone to triggering and slopes that get direct solar effect as temperatures increase could also be more suspect.  In areas outside our forecast zone to the south, with a shallower snowpack, you are more likely to find one of these large slabs. Don’t forget to use good travel protocol and consider consequences when choosing terrain.

Snowmachine triggered avalanche in Lynx Creek yesterday. Check out the spots where the avalanche potentially stepped down to older layers in the snowpack. 3.6.20.