Turnagain Pass

Yesterday a group found ‘touchy wind slabs’ on a Southeast aspect of Seattle Ridge near Bertha Creek Campground. These hard slabs were 3-10” thick, and formed on top of loose faceted snow and surface hoar that hundreds of people have been skiing and riding on this week. Moderate Northwest winds have channeled through some terrain in our forecast zone, but not all. Many folks have continued to get into steep terrain without incident  where snow conditions remain generally stable. These reactive wind slabs are an example of unstable snow that can be found on some terrain features. Today will be the last sunny day before a big weather pattern shift. If you’re headed into the mountains identify wind-affected snow that looks smooth or pillowed. Hard supportable snow that sounds drum-like should be suspect and could allow a person onto it before a slab releases.

Practice safe travel habits, such as exposing one person at a time, watching your partners and grouping up in safe zones. These are key ways to minimize risk. Ease into steep terrain and factor in the consequences should you encounter a wind slab or one of the following:

• Glide avalanche:  
• Identify glide cracks and avoid spending any time under these features. Glide cracks are opening and have avalanched within the last week. Glides are completely unpredictable and not human triggered.
• Persistent Slab avalanche: 
• Triggering a slab deeper in the snowpack is unlikely, but not out of the question in complex terrain. A layer of buried surface hoar 1-3′ below the surface has been mostly unreactive or hasn’t been found in most test pits over the last week.
• Cornice fall: 
• Remember cornices often break farther back from ridges than expected. Give them a wide berth.
• Loose Snow Sluffs:
• Be aware of fast moving surface snow in steep terrain. Sluffs are slowly becoming larger as the cold weather weakens surface layers.

Looking South from Center Ridge yesterday. The terrain in the Sun, SE shoulder of Seattle Ridge remains suspect for reactive wind slabs. This is a common area affected by NW wind direction. 

Loose snow surface conditions and glide cracks on a SW aspect of Sunburst yesterday. Close up of surface hoar, a possible weak layer lurking under isolated wind slabs. Photos by Kyle Van Peursem

South of Turnagain – Lynx Creek/Johnson Pass/Summit Lake zone:  A poor snowpack structure exists in these areas. The buried surface hoar that we have been talking about over the past week has been found as well as facet/crust combinations in the bottom of the snowpack. The last avalanche cycle was during the New Year’s storm, and overloaded a variety of these weak layers in Summit Lake. Cold weather this weak has been helping stability around the area, but localized NW winds this week may have added additional stress. Steep slopes without old debris below remain suspect. If you’re headed this way, the snowpack becomes more complex – evaluate terrain exposure and the snowpack as you travel.