Montana

We observed this avalanche from a distance. There was 1 involvement; initiated from wind affected, steep entrance into a loaded slope. Rider was carried approx. 50m on slab, deployed airbag and was able to ride off of the slab near some large trees. The thickest part of slab appeared to be 70+cm. We had previously skied an adjacent slope. At the top of that slope (very near to where this slab was initiated) we found hard and resistant but very planar hand shears down 25 and 35cm on stellars over low density snow. We did not observe surface hoar, but failures correlate with Dec 26. We also observed windslab and felt drumming in the snow adjacent to the crown.