Turnagain Pass

The majority of avalanche activity observed within the forecast area over the past several days of clear weather have been dry loose avalanches releasing in very steep terrain or small storm slabs releasing at the interface with the old snow surface. However, there are some notable outliers on the periphery of the forecast area in the upper elevations of Girdwood Valley (see ob here). The largest of these outlier avalanches released at high elevation around ~5,000′ on NW aspects (see problem 2 for more information).

Small storm slab and dry loose avalanche activity in very steep terrain in Seattle Creek area. Photo 12.21.23

Massive avalanche crown in the Upper Milk Glacier area near Crow Pass. Possibly due to a layer of facets deep in the snowpack from early season storms at upper elevations. Photo George Creighton 12.21.23

We are gaining a whopping 3 seconds of daylight today, and along with the return of the sun comes the return of stormy weather. Cloud cover, wind, and snowfall will increase throughout the day as a storm system enters the forecast area. Wind speeds are expected to increase from averages of 5-15 mph this morning to 15-25 mph this afternoon to 40-60 mph this evening.

Given the soft snow currently sitting on the surface, the increasing winds will rapidly build wind slabs in exposed areas and will make human triggered and natural avalanches 1-2′ deep possible. The likelihood of triggering a wind slab will depend on the timing of the incoming storm. The easiest way to identify areas where wind slabs are forming is to watch for plumes of snow being transported along ridgelines and feel the snow surface as you approach wind exposed areas. Feeling firm and hollow snow on the surface, seeing shooting cracks on steep features, or triggering small avalanches on test slopes are strong indicators that you are entering an area that could produce a wind slab avalanche.

In sheltered areas dry loose avalanches are likely in steep terrain and we recommend having a plan to manage your sluff before entering steep terrain.

Dry loose avalanches in the foreground and the upper Girdwood Valley covered in a blanket of snow, waiting to be blown around by the incoming winds! Photo Peter Wadsworth 12.21.23

We are continuing to monitor the layer of facets over the Thanksgiving crust, which is now buried 3-5′ deep in the majority of the forecast area. Recent observations from Turnagain Pass indicate that the layer remains stubborn to trigger and we are not aware of any human triggered avalanches on this layer in the last two weeks. However, in areas with a generally thinner snowpack, like Crow Creek in Girdwood and closer to Summit Lake, there have been observations of large natural avalanches during the storm cycle early this week. In these areas triggering a very large persistent slab avalanche 3-5′ deep is more likely and we recommend sticking to lower angle terrain if you want to avoid this problem.

We have very limited information about higher elevation terrain above ~4,000′ and there were several large avalanches observed at these upper elevations in Girdwood Valley yesterday.  These avalanche likely released earlier this week during the last period of snowfall. It is possible that there are weak layers near the base of the snowpack from early season snowfall that exist at these upper elevations but do not exist in the majority of the forecast area. As always, we recommend approaching new terrain cautiously and evaluating the snowpack before committing to steep terrain, especially in areas on the margin of the forecast zone where information is sparse.

Glide avalanches continue to release and new glide cracks are opening up across the forecast area. It is important to be aware of any glide cracks above you and try to minimize exposure time underneath them. These avalanches release spontaneously and can be very large and destructive.