Chamonix Couloir Avalanche

Yesterday a natural dry/loose avalanche ran in the Chamonix couloir in East Rosebud, partially burry all four people in my party and one person in a party above us. Four of the five of us were able dig ourselves out and there were no significant injuries.

We knew the area had received a lot of snow in the last week but there was only a four or five inches of fresh snow at the lake. At about 8,700 feet, when we transitioned to boot packing, there was roughly a foot of low density fresh snow that was bonded well to the existing snow. Skies were clear at sunrise, clouds moved in throughout the morning and it began snowing lightly around 11:30.

We didn't see the beginning of the avalanche, two members of the party above us said that a sluff that ran off one of the walls above them and was small enough when it ran past them that it didn't effect them. I don't know how high they were above the third member of their party but the third member was a few hundred feet above us. By the time the avalanche reached us it had grown substantially and was an over-head wall of snow. The two skiers who saw the avalanche start didn't see it step down to any deeper layers, it was just the new snow. Based on the data from my watch, we were carried about 750 vertical feet. We didn't take any photos of the slide.

The other party in the couloir may submit a report as well. Let me know if any additional details could be helpful.