Avalanche: Hatcher Pass

Trigger: skier - near rock out-cropping at ~2/3 way down.
Soft Slab at the interface of recent storm.
Fractured ~50 feet above, then propagated up, then across the slope skier's right.
The slide ran to the creek at the bottom of Valley of Sin, and roughly 50ft up the opposing side

We had reached the top of Hatch peak again after 2 laps (N facing, then W facing in the 4500-4000 ft altitude band - both in soft, unconsolidated snow).

We’ve annotated the image taken from the helicopter of our route. We dropped 1 at a time; first at roughly 3:15pm. Each skier followed a very similar course on the SE aspect. The skiing was loose powder, without significant crust. However, we did notice significant melt and worrisome (for wet slide) sloughing of the pure S facing snow near where the first two skiers stopped left of the gullies to spot. The avalanche occurred slightly after when the 3rd skier had passed the rock band (annotated star; I think roughly 3500 feet). The avalanche released ~ 50 feet above the skier (see attached photo which is taken right upon release). It propagated up, over, and then to the skiers right. The skier initially attempted to escape skiers right, then saw the slope ripping out above, and was able to get back to the high ground between the main slide paths. Miraculously, none of us were caught or carried.

A few decision-making take aways that might be helpful for folks to think about:
-We miss judged the amount that heat had influenced the snow structure at lower elevations while we were lapping higher.
-The lack whoompfing or snow movement on prior laps (and a similar track down valley earlier in the afternoon) reassured us more than they should have – this particular problem wouldn’t have given us direct signs of collapse until we were in a location to trigger it.
-It’s harder to make decisions about low(er*)-likelihood, higher consequence instabilities than higher-likelihood problems. We had discussed misgivings from signs of heating at the top, but decided to go.
-We're as guilty as anyone about sometimes being lackadaisical about choosing stopping/spotting locations with enough distance/geography to protect in the case of a slide with significant propagation. We were very fortunate to have chosen a good one this time (and being extremely lucky in how/where the snow fractured in relation to the skier).

None. We’re also extremely grateful to the folks who have worked hard on the forecasts and who jumped quickly into action - it was miraculous and purely chance that this ended the way it did.