Turnagain Pass Avalanche Forecast

The bulk of the approaching storm is not forecast to impact the area until late tonight into tomorrow. Yesterday we received a trace of snow which fell on top of surface hoar and near surface facets that formed over the past weak. This barely buried weak surface snow could become a concern as snow accumulates, especially in terrain that has a melt-freeze crust or wind hardened snow below the weak snow. Today it will be important pay attention to the weather and changing conditions. Shallow storm slabs may quickly form in the Alpine as snow falls and the wind increases.  Watch for blowing snow, cracking below your skis or machine and use small test slopes to assess whether the new snow is bonding to the old snow. 

Finding an old isolated slab especially in upper elevation terrain in Girdwood, Portage or Placer is not completely out of the question. This part of the advisory area received more snow in the last storm. There has been one known human triggered avalanche that failed in the facets below the new snow, which was last Thursday in the Placer Valley. Low danger before the storm does not mean no danger. Practice good travel habits, such as exposing one person at a time, watching your partners and grouping up in safe zones are key ways to minimize risk. Ease into steep terrain and factor in the consequences should you encounter one of the following:

• An outlier slab avalanche: 
  • Triggering a slab avalanche would most likely occur on an exposed ‘unsupported slope’ that sits above a cliff or steep rocky terrain. An old wind slab or a pocket of buried near surface facets and/or surface hoar 5″-2′ below the surface may be lurking in an isolated area.
• Glide avalanche:  
  • Identify glide cracks and avoid spending any time under these features. Glide avalanches are completely unpredictable and not human triggered.
• Cornice fall: 
  • Remember cornices often break farther back from ridges than expected. Give them a wide berth.
• Loose Snow avalanche (sluff):
  • Be aware of fast moving surface snow in steep terrain. 

Treeline surface hoar on Tincan, 1-20-19. Photo: Troy Tempel

South of Turnagain – Johnson Pass/Summit Lake zone: A poor snowpack structure exists in these areas.  Multiple mid-pack weak layers of facets and buried surface hoar have been found as well as a facet/crust combination in the bottom of the snowpack. No recent avalanche activity and calm weather has allowed the pack to slowly adjust. However, it still important to evaluate the terrain and snowpack. Upper elevation terrain with hard, wind-affected snow over the buried weak layers is the most suspect.