Avalanche: Turnagain

Original Observation: 

This skier-triggered avalanche happened on a southwest aspect of Cornbiscuit. It failed on either a buried layer of surface hoar or recently wind-drifted new snow from the previous 2 days.

The main S facing chute on Cornbiscuit ( ie go to high point then drop down 30ft, fall line South or nice wide fall line couloir N). # tracks were in main gut, I pushed the skin track higher up the ridge and stopped about 30 feet from high point because snowpack went to breakable/facets/crust, we ( 2 people) skied slightly skiers right of where I stopped and a group of 5 skied our line immediately after us.

Total tracks wiped out =10, for those that still think ski tracks say anything. about 30 or 40 minutes later @14:17 we saw and heard huge slide, rushed back to scene and did a search. We could see 2 people up on ridge but couldn’t understand what they were saying, hence the search. Turned up nothing. Skied out.

Meet the 2 guys who triggered slide in parking lot, they hadn’t wanted to come down bed surface because they were scared of shooting cracks in hang-fire. They said they pushed my skin track another 10 feet and triggered everything, they said 3 foot crown in gut and 1 foot everywhere else, it looked like more from below, but didn’t do a profile.

The propagation was surprising, maybe 20ft skiers left in shallow snow ( from trigger point) and 150ft skiers right following skin track and taking out the gut and wrapping past that.

Subsequent Observation from another party:

Skinner triggered avalanche occurred while I was skinning up Cornbiscuit (with one other person).  I triggered the slide from near the ridge. no one was caught in the slide.

At least 7 people had already skied the slope and had recently cleared the runout zone (they all came back to help search).

Fracture propagated from rocky area near the high point in the  ridge, above and below the trigger point. Check out the picture  looking back down at the major saddle. (look closely – the  remaining snow above fracture has a series of shooting cracks).

We were not able to get below the crown face to look closely.  Had to ski out to the north.

Estimated crown depth: 12″ – 36″.
Estimated slide width: 300-500 feet.
Dust cloud appeared to cross the valley all the way to Lips.

No other avalanche activity, whoomphing, shooting cracks noticed  prior to the slide. except near the saddle, snow did not seem to  be heavily wind or sun-effected (seemed unconsolidated), so it  surprised me that it propagated so far.

Subsequent Observation from a 3rd party:

I was skiing on Corn Biscuit today and witnessed an avalanche on a south facing  slope. There were no obvious signs of avalanche activity during our skin up the west  slope or in our test pit (southwest slope). We made our first run down the south west  facing slope and then headed back up for a second run. Our group traversed further  down the ridge, following the skin track of a group of two in front of us. Feeling fairly confident with the snow pack we decided to try our second run down this (south). slope.

The group of two were the first to go, they skied one at a time down the slope  and traversed to lookers left, our group followed suit. After finishing our run the group of two traversed up the valley and our group headed west, out of the valley. It was during our traverse out that one of our groups members looked back and saw a huge plum of snow from an avalanche that had just released. We immediately turned around to search the debris, because there were other skiers in the area. When we arrived at the scene we realized that the avalanche had released from the slope that we had just finished skiing. The crown face looked to be approximately 150ft long with depths varying form 1ft to 4ft. The runout traveled down into the valley and up the opposing slope.

We were able to communicate with two skiers at the top of the ridge, who had triggered and witnessed the slide. According the them there weren’t any people caught in the avalanche. Just to be safe our group fanned out and combed  the area with our beacons. we searched for approximately an hour before we  concluded that the scene was safe. we also met with the group of two that had also  witnessed the slide.  After discussing the days events we skied out of the valley and  down to the cars. There we met with the two skiers who were atop the ridge.  According to them they had traversed just 10 ft past the end of our skin track when  the avalanche released.

I cant speak for the group but these are the mistakes i made:
1) relying on one test pit from a slope with a different aspect.
2) not being cautious enough after a storm cycle.
3) relying on someone else’s observations and not making my own