Toured from WMR resort boundry past Ghoulie point, towards " Kona".
SS-Su-R2-D2. Below Ridge between Ghoulie Point and "Kona", 6,400 ft, NNE, 38'
Group of 3 experienced skiers. Avalanche was triggered by 3rd skier on slope. Skier traveled between 2 tracks placed by first 2 skiers in the group, which were approx 15 yards apart. Skier remained on their feet and was pinned against a tree w/ skis on by debris. Skier required assistance with shovels from other members of party to escape entrapment between snow and tree. 2 other members of group traveled uphill and were with skier who was trapped within 5 min of accident.
This location appeared to have developed more of a slab than other slopes w/ same aspect/ elevation in this area that we skied today and in the prior week.
Observations of our group: We discussed our concerns and awareness of the surface hoar layer and discussed that we had not observed slab formation in recent days, and we felt confident that we would find a relatively stable snowpack in the terrain we planned to ski. 1 member of the group had skied similar terrain in nearby locations with similar elevation/ aspect multiple times this week and saw no signs of instability. We made a plan for the day as a group, we discussed our plan to ski 1 at-a-time and to maintain visual and verbal communication. We did not discuss slope angle management as part of our pre-trip planning. I performed multiple "hasty" hand pits during our tour, including our uptrack towards this slope which was on an adjacent slope with similar aspect and slope angle. I found no slab formation on top of the buried surface hoar and we saw no signs of instability prior to the avalanche.
Reflection: We exposed ourselves to a slope with a slight convex roll over that was relatively open, with few trees in a 100sq/ft area - this likely influenced surface hoar development/ preservation and slab formation in this specific piece of terrain. We did not perform a hasty or more formal test on this specific slope before we skied it. We did use safe travel and communication strategies and were able to respond to the trapped skier quickly.
