Turnagain Pass

A surprise pulse of moderate winds came through the area yesterday from around 10 am to 11 pm which created fresh wind slabs at upper elevations. Unfortunately, the Sunburst weather station stopped reporting just as these winds kicked up so we are in the dark about the exact speeds and duration in Turnagain Pass. Weather stations near Grandview and Alyeska reported similar increases in wind speeds yesterday with averages of 10-20 mph and gusts of 20-30 mph for about 12 hours. Clouds lingering in the area also produced 1-3″ of new snow in Turnagain Pass and Portage/Placer area, with no measurable new snow in the Girdwood area yesterday.

The primary avalanche problem today will be wind slabs created during the period of elevated winds yesterday which will be possible for a person to trigger today. These could be up to 1′ deep depending on how much soft snow was available at the surface for the winds to transport. The most likely area for deeper wind slabs are upper elevations on northerly terrain where dry snow still remained on the surface yesterday. These wind slabs formed on top of buried persistent weak layers and the added load could make deeper weak layers more reactive (see problem 2 for more details).

Wet Loose Avalanches: The forecast is for mostly sunny skies today, which should give the sun enough time to warm up the snow surface and create prime conditions for roller balls and wet loose avalanches. These are typically not large enough to bury a person but they can be more forceful than expected, especially if they catch you off guard in steeper terrain.

Cornices: Solar warming on cornices can cause natural cornice fall or weaken them to the point where it is easier for a person to initiate a cornice fall. We have some chunky cornices across the forecast area right now, so be aware of travelling underneath them if they are heating up in the sun and give a wide berth when travelling along ridgelines.

Glide: The warm temperatures the past few weeks have helped awaken glide cracks, with new ones opening up along Seattle Ridge near the uptrack, Tincan ridgeline, and Eddies. As always try to minimize your time spent underneath these because they can produce very large avalanches and are completely unpredictable.

While the fresh wind slabs are the most likely avalanche for a person to trigger, the presence of buried surface hoar and near surface facets in the upper 2′ of the snowpack should be the driving factor in decision-making practices today. Over the weekend there were two reported near misses from Turnagain Pass where the 4th skier on a slope triggered an avalanche on a persistent weak layer. In one of those incidents we know that a very experienced group actively searched for the buried surface hoar in the area they were travelling and did not find it before triggering the avalanche on the descent. This should be a real wake up call for all of us that buried surface hoar can be difficult to find even by an experienced person and has the potential to produce large avalanches on surprisingly low angle terrain.

Both of the recent near misses occurred in high elevation terrain on northern aspects in Turnagain Pass. That is a good indicator of the most likely place to trigger an avalanche on these persistent weak layers, but it does not mean that it is impossible to find a reactive pocket of these weak layers in another location. We recommend conservative terrain selection and careful snowpack evaluation if you decide to enter avalanche terrain today. To minimize the exposure of your group, remember to only expose 1 group member at a time in avalanche terrain, always spot your partners, and group up outside the runout zone on the descent. To avoid this problem all together stick to lower angle terrain and lower elevation slopes.

Clouds and light snow lingering over the area yesterday, while surprise winds created fresh wind slabs at upper elevations. Photo 3.13.22

Wet loose avalanches on steep southern terrain are expected as the sun warms up the snow surface today. Photo 3.13.22