Waterhouse Avalanche Investigation-Jan 31

We went to Waterhouse Peak on Luther Pass to investigate an avalanche that was reported on Sunday Jan 31 at 2:30pm.  The original submitted observation is here:  https://www.sierraavalanchecenter.org/observation/2021/jan/31/0230/waterhouse   Given its location within the terrain, we were very interested in seeing if this avalanche could be associated with one of our persistent weak layers causing a deep slab avalanche.  We tracked down the avalanche from the location in the observation and were able to find it at 8970' on a E aspect, just below the ridgeline in below treeline terrain.  We saw wide propagation, a deep crown line, and lots of uncovered obstacles on the bed surface of the avalanche.  It was immediately clear that this was a deep slab that failed on one of our persistent weak layers in the snowpack.  We did a crown line profile-see snowpit.  This avalanche failed on near crust facets that were buried just below the Jan 22 rain crust and sandwiched between 2 crusts.  The crown on this avalanche ranged from 2.5 to 4' deep, was 150' wide and ran downslope 300'.  The crown went across the slope from trees to rocks and propagated into steeper terrain and also had shooting cracks that went off into lower angle terrain.  The crown line of the avalanche measured 35 to 38 degrees in steepness and was in a steeper pocket of terrain with adjacent terrain less steep.  Where this avalanche occurred is densely treed with lots of granite rock.  Below the Jan 22 rain crust was around 1' of snow that was weak and faceted to the ground.  Exposed rock and bushes were visible throughout the bed surface.  Although relatively small, this avalanche path could have had huge consequences and we are very thankful that this group made it out of this event unhurt and alive.