Skiing down the ridgeline and moved leeward around a minor windroll.   I immediately collapsed the slope - hard slab over facets and

Bill Nalli, Provo UDOT forecaster is standing at my trigger point (where the slab was only 45cm deep).  Momentum (always your friend) carried me skier's left where the the hard slab 5' deep broke above me, and I was carried down the slope.

Another view, looking back up to where it initiated there left of Bill where it was 18" deep, then propagated to up to 5' deep.  I had no chance. 

Looking down the ridgeline to the west north-west.   Looks like it propagated 600-700' wide.  Stiff slab = longer propagation.  Soft slabs tend to break at your feet (lacking a persistent weak layer); hard slabs have so much internal strength that they propagate above you and over farther distances.  Ever notice how you'll get a ECT30 or CT 30 (or more), but when it fails, it pops out like a cash register?  It's the same.  Note also from the pic that it literally pulled all the way up to the ridgeline.  That is - had someone been standing on the flats ridge, the carpet would've yanked them down the path.