Turnagain Pass Avalanche Forecast

There were no new avalanches reported yesterday, but it is likely there was some natural activity with the new snow and strong winds. Hopefully visibility will improve enough to get a better eye on things today.

Yesterday’s storm brought 6-10″ low-density snow to the area, with easterly winds blowing 30-50 mph and gusts getting up to 75 mph. The system is moving out this morning and we should see fairly quiet conditions by the middle of the day, but all of that wind and new snow will make it likely a person can trigger a large avalanche even as the weather is calming down. If you are out traveling in the mountains today, keep a few things in mind:

• Temperatures were warming throughout the storm, stacking up warmer, heavier snow on top of colder, drier snow. This ‘upside-down’ setup may make it a little easier to trigger an avalanche within the storm snow.
• The strong winds have been building reactive wind slabs, especially at upper elevations. Even though we only got 6-10″ snow, we can expect these slabs to be 1-2′ deep or deeper. Be extra cautious around steep slopes just below ridgelines, convexities, and steep gullies.
• At the mid and lower elevations, the storm snow buried a surface crust that went up to somewhere between 1500′ and 2000′. We’re not quite sure how that interface will behave today, but it should be a layer to watch out for until we have a better idea of how well the new snow is bonding.

Avalanches are most likely during and immediately after a storm, which is exactly where we will be today. If the snow and wind hang around longer than expected today, expect to see the avalanche danger rising. In addition to those problems within the new snow, remember we have a problem layer buried about 2-4′ deep now that has the potential to make even bigger avalanches. More on this in problem 2 below.

We’ve been concerned with a layer of buried surface hoar for several weeks now. After yesterday’s storm, the layer is now buried somewhere around 2-4′ deep. This is the first loading event the layer has seen in over two weeks, and though it’s not a huge dump, it is pushing the needle towards instability. We should be treating this layer with a little extra caution for now, until we get a better idea of how it is responding to the new load. This is another good reason to tread lightly today, avoiding spending time on or below steep terrain.

This avalanche in the Summit Lake area failed on a weak layer in the upper snowpack and was likely triggered from low on the slope. Although this is outside of our advisory area, it is similar to the kind of activity that we can expect at Turnagain Pass and Girdwood today. Photo: Ryan McLaughlin, 02.04.2023

We haven’t forgotten about the problematic facet/crust combination buried 4-8′ deep in the snowpack. It is unlikely the new snow from the past 24 hours will be enough to significantly impact this weak layer. It is still unlikely a person will be able to trigger an avalanche this deep in the snowpack, but if you were to find a spot, it would be in an area with a thinner snowpack, and it could propagate across multiple terrain features on multiple aspects. Because of the small likelihood of triggering one of these very large avalanches, the more concerning issues for now still lie in the upper 2-4′ of the snowpack, and that will be enough to keep us out of big terrain for today.