Reactive Wind Slab Avalanche on Lincoln Ridge

We went to Lincoln Ridge off of Yuba Pass to look and see if the recent buried surface hoar, that was the cause of another avalanche yesterday, was still present and reactive in other mid elevation areas.  We dug a snowpit in open below treeline terrain to look for the buried surface hoar layer which was easy to find 1 foot deep below the snow surface.  The layer was very apparent with a distinct line across the pit wall with the surface hoar up to 10mm + in size.  We got 2x ECTP-13 on the buried surface hoar layer.  Snowpit location 39.59323 -120.49231, at 7480' on a NE aspect.

We traveled up to the ridge where strong to gale force SW winds were blowing snow.  On a wind loaded test slope, we were able to drop an oven sized chunk of cornice onto the slope and cause a wind slab avalanche to fail.  This wind slab avalanche was 1-1.5' deep, dense, and propagated wide with shooting cracks off into lower angle terrain.  On the bed surface of this wind slab were cracks that stepped down to the buried surface hoar layer.  Since this was a relatively small test slope with good compressive strength, it did not cause an avalanche down to the buried surface hoar layer.  In larger terrain, it is thought that a similar avalanche would step down 3' and cause a much larger and destructive avalanche associated with this persistent slab problem.  Avalanche location is at pin drop on obs map.

Heavy surface snow existed at the higher elevations in this area with wet and sticky snow below 7200'.