Vail & Summit County
AvalancheAnonymous · Mar 4, 2023 · Vail & Summit County
Weather
Relatively calm. Forecasted winds had not yet arrived. Temps in the mid 20's (estimated). HS measured at 220cm at top of slope. Measured again at 205cm mid slope after avalanche took place.
Snowpack
No formal snowpack obs were preformed. Boot pen was about 15cm with the snowpack underneath feeling very cohesive. Pole tests did not reveal any significant layers in the upper snowpack, except on aspects exposed to solar which held a melt freeze crust. Wind loading was evident in many places. Persistent weak layer was not observed prior to the avalanche, but was obviously evident based on what happened.
Avalanche
2 groups were present in the area, ours and another. We started our tours at similar times, talked about each others plans, and shared radio channels. Group A (their group) was a group of 4. Group B (our group) was also a group of 4. Group A and B both arrived at the top of the intended slope at the same time. We decided Group A would ski the slope first while Group B would ski a different slope, tour back up, and then ski the originally intended slope. Group A skied the skier's right side of the slope to the right side of small ribbon of trees with no incident. Group B skied our alternative first slope with no incident and toured back up to the top of the main intended slope. Group B discussed our approach to the slope and decided to ski the upper slope one at a time and move slightly left of Group A's tracks. Skier 1 dropped and skied until encountering a convex roll where he pulled off to a safe spot on the right side of the slope, the remaining 3 skiers met and regrouped there. The group decided to continue skiing the slope. Skier 1 went first again, and skied the slope without incident, pulling off at another safe spot below. Skier 2 skied about 10-15 feet skier's left of skier 1's track and made about 5 turns before triggering a large persistent slab avalanche. Skier 2 saw the avalanche crack quickly before it gained too much momentum and was able to ski out of the path skier's right. After the debris settled, skiers 2,3, and 4 all regrouped at the bottom of the slope and debriefed the event. We took another HS recording, took some pictures, aspect, elevation, estimated slope angle, then skied the remainder of the slope and used group A's skin track to ascend back to the top. Group A radio'd Group B with some beta about the skin track, at which time Group B informed Group A of the avalanche. While skinning up Group B was informed that Group A had also triggered a smaller avalanche on the slope that Group B had skied first. The second avalanche that Group A triggered appeared to be a wind slab, with new snow on top of it, that slid on a melt-freeze crust.