Turnagain Pass Avalanche Forecast

• Girdwood: Multiple natural avalanches ran in paths along the Seward Highway between Bird Point and Peterson Creek as strong winds loaded start zones yesterday. Many of these ran to sea level. Skiers on Notch easily triggered avalanches in the new snow on small and steep terrain features.
• Turnagain Pass: We received word of a skier-triggered wind slab avalanche on Eddie’s yesterday. We do not have any details on the size of the avalanche, but it sounds like nobody was caught or carried.

The much-anticipated storm arrives in force today, with strong winds and heavy snowfall expected through tonight. Some areas (Portage/Placer and Seward) may see 2-3′ of snow, while the core of the advisory area is going to be on the low side of storm totals, with only 4-8″ snow expected by tomorrow morning. We saw natural avalanches yesterday as winds were blowing 15-35 mph with gusts up to 68 mph. We can expect more today as snowfall picks up and winds increase to the 20-40 mph range, gusting 40-60 mph. This combination of new snow and strong wind will make sensitive slabs that fail naturally today, and are likely to step down to deeper weak layers in the snowpack, resulting in very large avalanches (more on this in problem 2 below). These avalanches are expected to run long distances into runout zones at lower elevations. Travel in and below avalanche terrain is not recommended today, including nordic and hiking trails that will be exposed to avalanche hazard from above.

Skiers saw sensitive conditions on Notch yesterday as winds picked up, with multiple shooting cracks and soft slabs releasing on small terrain features like the one pictured above. Photo: Kakiko Ramos Leon. 12.05.2021

Although this storm may be somewhat unremarkable on its own by Chugach standards, it will likely be the extra load needed to make very large avalanches on an already dangerous snowpack. Strong winds and new snow will add a lot of weight to a snowpack supported by multiple weak layers, likely pushing them to their breaking point. As we saw towards the end of last week, these weak layers were already capable of producing very large avalanches (take a look at this avalanche from Eddie’s or this one from Magnum for a reminder).

These weak layers have been propagating long distances, and people have been triggering avalanches remotely- from above, below, and to the side of steep slopes. With the added potential for natural triggers, avalanche conditions are very dangerous right now. Very large avalanches are expected to run into flat terrain below steeper slopes, which means users like hikers, bikers, and nordic skiers need to be aware of the overhead hazard. Long story short, today is really not the day to try to get out in the mountains.

Large natural avalanches like this one on the Karlsberg path on Orca from last week are on our mind today. Similar activity is expected as winds continue to load a dangerous snowpack. 

As if we didn’t already have enough to worry about with wind slabs, storm slabs, and persistent weak layers, we are also still thinking about the potential for large glide avalanches. Glide avalanches are impossible to predict, but the rapid warm up over the past 24 hours is not likely to improve the glide condition.