A skier triggered the avalanche from a milder slope above, which was connected to the problem slope. The crack propagated over quite a large distance and enough snow was released to bury or injure a skier. Some of the snow piled quite deep in front of trees along the avalanche path, which could have been a serious situation for any body caught in those spots. Fortunately the slab wasn't too deep at most 1ft at the deepest points.
Signs of Unstable Snow
Did you see shooting cracks?
Did you experience collapsing or whumpfing?
There is a thin layer of surface hoar that is buried (less than a foot deep) in some locations with potentially wind slab or storm slab on top of it. This creates a very unstable situation with observed avalanche and shooting cracks in those locations. It seems that W/NW aspects are more affected. I didn't find that same problem on South facing slopes. My snow pit on a south facing slope didn't reveal any major instability, but that could just be because the surface hoar got blown away in that particular location.
Observed Avalanche Problem #1:
NW slope a few inches to a foot deep with potentially surface hoar underneath