Turnagain Pass

Cooler weather and a chance for a few snow flurries above 2,000′ should keep most of the springtime rapid warming at bay this weekend (and possibly into next week). That said, we are still seeing a handful of avalanches each day as the snowpack transitions from dry to wet. Most of these have been relatively small wet loose sluffs and glide releases. The most notable however, is a natural wet slab avalanche that occurred Thursday(ish) in the Girdwood Valley (photo/description below). This slide was on a Northerly aspect around treeline and illustrates how all aspects are suspect currently. During the past 2 days there has been some type of avalanche documented on North, West and South slopes (I’m betting there is an Easterly one out there as well).

The key for a safe day in the mountains is knowing what slopes are wet, saturated and unsupportable (unstable and dangerous) and what slopes are frozen (stable). This is not always as easy at it seems. Carefully monitor surface crusts throughout the day and be aware of steep terrain above you that may be heating up faster than you may expect. Steep rocky terrain baking in the sun can begin to produce wet sluffs, which could in turn trigger a wet slab, and send debris to valley bottoms where the surface is still frozen. 

WET SLAB, WET LOOSE and CORNICE FALLS – things to keep in mind if you are headed out: 

1. Are you seeing recent avalanches?
2. Is the snowpack frozen or wet and soggy?
3. Are you punching through a shallow crust into wet soggy snow? A shallow re-freeze is still weak and could avalanche.
4. Are you in a runout zone? Can an avalanche releasing above wash debris over your location?
5. Buried weak layers in the pack can make a small avalanche or sluff larger by propagating across the slope and/or stepping down.

Recent large slab avalanche on Orca Ridge/Big League, North aspect – released sometime close to Thursday, April 27th. This slide looks to have started as a wet loose avalanche then stepped down to the mid-pack and then again to the ground around 1500′.

Skier triggered wet loose sluffs on the Southwest shoulder of Sunburst from Thursday/Friday (old crown from early April storm cycle in background)

Farthest left natural wet loose avalanche on the West face of Magnum is also from Thursday/Friday (April 27/28), many older dark and melted out loose snow avalanches from earlier in the week on the right of the face 

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Glide cracks are also opening up and releasing on many slopes in the region with the springtime melt-down. At times it can be difficult to tell the difference between glides and wet slab avalanches. But that is beside the point – both are dangerous. The way to manage glide avalanches is to stay out from under any slopes harboring glide cracks! Check out the photo below from the motorized up-track. This slope is notorious for producing glide avalanches. Additional glide avalanche activity is expected today and through the week.

Note the opening glide cracks lower on Eddies West facing slopes?

Recent large glide avalanche on the lower Southwest facing Tincan terrain – in this area several glide cracks have released while several cracks and hanging in the balance.

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There are several buried persistent weak layers in the snowpack; ranging from buried surface hoar 2-6′ deep, mid-pack facets and facets near the ground. Shallow snowpack zones such as the Summit Lake area harbor depth hoar near the ground. On upper elevation North, West and Easterly aspects these weak layers could re-activate when the snowpack melts, becomes saturated and loses strength. If significant warming/melting occurs this weekend or into the workweek, keep in mind large slab avalanches are possible – both triggered by a person as well as naturally.