The slide occurred on a NE facing wind packed slope. I was skiing with a guide. We had ascended from the SW on skins. There was no previous evidence of recent slides. It was early season and there had been fresh snow and wind for the previous two days.
We skied out under the rock face at the very top of the slope and began the descent from approximately 2,500 meters. It was a short distance to the edge of a cornice (ten or fifteen turns or 50 meters) my guide went first to the left edge of the cornice to investigate conditions. After a short while he signaled me to follow. I started down right next to the guide's tracks. Five turns in I heard the guide shout my name. I looked up to what appeared to be a wall of loose snow 2 meters high and a half meter standing wave of dense snow at it's base. The standing wave seemed to be moving toward me. In hind sight I was obviously moving toward it! It was a bit windy so I never heard a telltale crack or whumpf. My first alert to the danger was a shout from the guide.
Finally, I realized I was in the starting zone of a slide. At first I tried to ski out which proved futile. As I approached the cornice I gave in to the inevitable and started to prepare for the ride. I discarded my poles and went for the release handle of the ABS pack. I was wearing medium weight gloves and it took two attempts to get a good grip on the handle. The first shot was with my right hand alone. I mis-gripped and my hand slipped off. On the second try I went with both hands and got it quite easily. If I had had heavier gloves or mitts a one handed pull would never have worked. In the future I would go at the handle with both hands right from the start.
I felt the airbag deploy just as as I was going over the cornice. There was quite a drop over the cornice maybe 20 feet. I was falling straight down feet first for some seconds. I was completely covered in the snow pack so I couldn't see anything. The fall must have terminated into a pile of snow that had arrived from over the cornice before me. The landing was soft and I was stationary for a second or two but then in short order the snow from above started to pile on every thing went from white to black and got very heavy. At this point the snow pack started to move fast and began throwing me head over heals. I suspect that my bindings ejected on the very first rotation after the fall from the cornice. The rotations were deliberate, not fast and not slow. At the start of each rotation I could see the white of the snow all around but not the sky. The snow was light enough so I could push it away from my mouth, breathe and take a few breast strokes. At the bottom of the rotation it was completely black and the weight of the snow prevented any kind of movement. I went through 3 or 4 full cycles and then believe I was launched off a small cliff. Just before going over the cliff I was at the bottom of a rotation and then all of a sudden the weight was gone and I could see white. The rotation stopped I was in a prone position and feeling weightless but still surrounded by snow. After a few seconds I landed hard hitting a rock on the lateral side of my lower right thigh and knee.
After the impact I was stationary for an instant as snow started to pile on from above and then everything started to move quickly again. As soon as things got moving the head over heals rotations began as well. This time I went through 2 or 3 rotations just like the previous ones and was again thrown off another small cliff. I was launched in a prone position but this time the impact on rock was to my left knee and thigh on the medial side. After impact there was a slight pause as the snow pack compressed around me then back to freight train speed down the fall line. I felt one more rotation and then the slide started to slow. As the speed diminished my body stopped flipping and continued in a wave like motion from the prone position head first downhill. Then the avalanche seemed to come to an abrupt stop I was rolled onto my back and continued to slide until I came out of the snow pack on the valley floor completely uncovered.
Two notes of interest on the ABS pack. First, I believe the pack kept me flipping in the top of the snow pack and helped keep me coming back close to the surface. This allowed me to both get some breath and swim a bit higher through each rotation. Second, I think the pack helped me stay in a prone position when I was launched from the cliffs with my head up over my legs allowing my legs to take the impact instead of my head, neck or shoulders.