Turnagain Pass

The word on the street is Friday’s wind event…. Very strong winds from the West and South did a number to the snow surface, the snowpack and triggered numerous natural wind slab avalanches. Certain areas are stripped to the ground while others have sastrugi and rock hard wind drifts 2-3′ thick. In general, many slopes sport a variety of 4-8″ supportable wind slabs, thinner breakable wind crusts and even some soft snow in between. Don’t get too down though, there are zones that managed to survive and harbor soft settled snow, but folks seem a bit reluctant to give up the coordinates. The clear (but warm) weather forecast for the next week may start eating away at the hard surfaces and riding conditions could improve.  (Check out what folks reported yesterday HERE.)

PERSISTENT SLAB AVALANCHES (In our current case: Hard WIND SLABS SITTING ON WEAK SNOW):

What to keep in mind and watch for:

• Wind slabs are likely to be sitting on any number of weak layers (facets and/or buried surface hoar)
• Look for hard snow over soft snow – slabs can be strong enough to support the weight of a snowmachine or skier, allowing you onto them before they release
• Triggering a slab from below is possible
• Slabs on unsupported slopes in steep rocky terrain are prime suspects
• Listen for whumphing
• Look for cracking around your snowmachine, skis, board

It may be a busy New Year’s Day – remember safe travel protocols:

• Expose one person at a time
• Watch your partners
• Have an escape route planned
• Watch for other groups
• Consider, what will happen if the slope slides?

 
Photo below: Wind damage and older avalanche activity on Magnum’s NW shoulder

Large natural wind slab avalanche from Friday on the Northerly aspect of Magnum (back along ridge toward Taylor Pass). Crown mostly filled in, debris ran up other side of creek bed near common up-track to Taylor Pass.

Illustrating the complex nature of our snowpack and multiple weak layers:  The Alaska Avlanche School Level 1 course had a CT (compression test) that resulted in three weak layers failing simultaneously on the 21st tap! This is a rare test result (top 2 layers were buried surface hoar and bottom layer was basal facets) Details HERE.

Summmit Lake area: Anti-tracks on Manitoba Mtn. Similar to scoured areas in Turnagain Pass. (photo J Haffener & S Galoob)

Watch for cornices in unusual places from the Dec 30 wind event. Though these may seem rock hard and welded into place, it’s good practice to always give them a wide berth – we do have warm, sunny weather on tap and this can help to weaken them.

Friday’s Southwesterly winds across Sunburst ridge attempted to strip the large cornices formed by the predominately Easterly winds.