Turnagain Pass

It has been about two weeks since the last string of human triggered avalanches on our weak layer of buried surface hoar from 1/10. This past weekend the warm temperatures caused widespread loose snow avalanches. Some of these loose snow avalanches triggered slabs, one of which released on buried surface hoar on Goat Mountain in Girdwood Valley. That is the last avalanche activity we know of in the forecast region.

Another day of relatively calm weather in the forecast area with light snowfall (1-2″) and calm winds. Visibility will likely be the biggest challenge, with low elevation cloud cover expected to persist through most of the day before a brief clearing period this afternoon. Things will be changing tomorrow with strong winds and heavy snowfall expected, stay tuned!

Our primary avalanche concern continues to be a layer of surface hoar (1/10) buried 2-3′ deep that exists across the forecast area. Over the past two weeks this layer has been gradually gaining strength and we have seen less alarming results in our snow pit tests and much less avalanche activity. However, we call these ‘persistent slabs’ for a reason. It is still possible to trigger a large avalanche in areas where the surface hoar is well preserved. The most likely areas to trigger an avalanche are above 2000′ and in regions with a generally thinner and weaker snowpack where the weak layer is more accessible.

To avoid this avalanche problem we recommend sticking to lower angle terrain and being aware of any overhead avalanche terrain, especially if there are other groups travelling above you. Assessing this weak layer is getting more difficult as it gets older. It is harder to find in the snowpack (see photo below) and snow pit tests are less consistent. The best approach to identify and assess the weak layer is to dig a snow pit and use a compression test or extended column test to evaluate how reactive the weak layer is in your area. Unfortunately, even if you get stable results in a snowpit there is always some uncertainty with persistent weak layers. The only way to be sure to avoid this problem is to stick to mellow terrain.

In addition to our deeply buried weak layers, loose snow avalanches are possible in steeper terrain. We have had some incremental snowfall this weak that is adding up to enough volume where you could get a decent sluff moving in steeper terrain.

The 1/10 buried surface hoar layer near the crown of an avalanche that released naturally last weekend. Photo 2.2.23

The monster lurking near the base of the snowpack is still on our radar, even though it has been almost a month since the last activity on the Thanksgiving facet/crust layer which is now buried 4-8′ deep. We continue to see this layer in areas with a thinner snowpack, but it is unlikely to trigger an avalanche on it due to the strength of the snowpack above.