After decending the upper Tanners Couloir, and reapplying skins in upper apron of Tanners proper, had my back turned as I had begun to re-ascend narrow chute to the notch between Tanners and Broads Fork, heard this loud whoumping cascade....looked over my shoulder and was able to snap a pic of slide/powder cloud.  A lot of unknowns with the soft slab/large sluff...but there was a very weak layer of graupel resting above slick suncrust and 6in++ or so new snow accumulation, which in our pits tests 30min prior had been popping out on isolation with our shovel tilt tests, etc.  

  There was some light southwesterly winds with moderate gusts, which we believe triggered this natural.  Either from loading or from associated cornice fall.  the avalanche/sluff did carry a lot of power and had a fair amount of mass behind it.

Luck was with us today, but just a good reminder of good terrain and route selection at all times and dont linger too long in obvious avy paths....even if there had been no signs of instability prior.  good habits!