Toured up Alpental Valley and up big trees. Hand pits while climbing showed a couple graupel layers down approx. 6" and 12" However snow above these layers was generally light and not cohesive. Dug a pit on the (unicorn?) knob above big trees. Rain crust was 130cm down based on probing. We did not dig all the way down to the rain crust. Did a quick ECT which showed the same graupel layers in upper snowpack which failed but did not seem to propagate (only failed directly under shovel when tapping) and did not seem to have cohesive slabs. The rest of the top 2-3' of snowpack seemed overall pretty right-side up and stable. Did a run in big trees trying to test some of steeper bits under the cliffs on far skiers right. Overall skied great an no signs of instability other than some sluff. Toured back up to draft dodger. Where we watched Alpental patrol ski cut the skiers left side of the cleaver and get some relatively thin windslabs to release. None of these showed signs of stepping down or propagating in surprising ways. Dropped into our second run and triggered the slide described above. Skier was aware of the convexity and was moving towards a high point when it broke, away from the slide. Was able to arrest with the help of a tree and was not carried. Shortly after the slide got to the bottom of the feature (150' below) I heard a loud noise which I believe was the collapse of the lower slope. Once we saw how far the slide ran, we skied the slide path as quickly as we could (safely) and performed a beacon search of the debris, concerned that someone could have been below in the apron (hence didn't take pics or observe crown). I have noticed people transitioning and even skinning up under the hummocks apron and I am thankful no one was there today. This served as a serious reminder not to linger in that area. The debris ran essentially all the way through the flats (almost to the source lake skin track).