Turnagain Pass Avalanche Forecast

There was a very close call Wednesday on the Raven Headwall. A solo skier, on the final leg of the Eklutna traverse, was caught, carried around 800′ and buried to their shoulders in a large avalanche. They were able to self rescue and are OK. The skier triggered the slab on the upper mid-slope while descending. The slab fractured around 30-50′ above the skier. This appears to be a large wind slab formed by the strong northerly outflow winds on Tuesday and Wednesday. The wind slab may have been sitting on weak snow, allowing it to propagate across the entire headwall. We would like to thank the skier for telling their story and please take a moment to read their account HERE.

Large skier triggered slab on the Raven Headwall. 3.11.20. Photo: Anonymous

Close up of the crown face. This appears to be a wind slab that formed from the strong outflow winds Tuesday and Wednesday. 3.11.20. Photo: Anonymous

And…. it’s springtime. Light winds, warm temperatures and long sunny days are here. Starting today, we are on a warming trend that should last through the weekend and even into Monday. Not only does this weather invite trips into the far reaches of the mountains, it also invites a new factor for avalanches; sunshine and warming. We can’t let the hospitable weather lower our guard.

As we’ve been mentioning, there is a thin layer of buried surface hoar around 1-2 feet below the surface in many areas. Even deeper in places that saw significant wind loading mid-week by the northwest outflow winds, such as the Raven Headwall avalanche mentioned above. This layer has not been found everywhere, but has been prevalent enough that it’s keeping us concerned. It also may be sitting on a sun crust on steep southerly slopes, making it that much more reactive. That said, triggering a slab large enough to ruin our day is still very much possible. Keep a close eye out for stiff snow over softer snow and cracking in the snow around you. Watch for slopes with wind loading as these are the most suspect places to trigger a slab.

Sun Effect:  With light winds, direct sunshine and warm air moving in aloft we can expect solar aspects to warm dramatically over the next couple days. This change is a shock to our snowpack. It not only moistens the surface, creating easily triggered moist sluffs (and natural ones as well), but it can increase the likelihood of triggering a slab avalanche. It can also help to re-active older weak layers that sit very deep in the snowpack. In our case the January facets that are 3-6 feet deep. Will the sunshine this weekend be enough to do this? Probably not, but something to keep in mind as we move forward.

Cornices:  Avoid travel on cornices and move quickly underneath them. Remember, warming temperatures and direct sun are classic mechanisms for destabilizing these monsters.

Large cornice that sits on the north side of Superbowl (head of Cornbiscuit and Magnum). 3.12.20. Photo: Heather Johnson

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