Surface hoar slide

Ski cut sent a slide that failed on the known-to-be-reactive buried surface hoar layer . Avalanche broke around 12-14” deep, 100’ wide and ran around 100 yards. It was extremely sensitive.
We had skied a similar angle/aspect slope earlier and didn’t get any reactivity. Occurred around 9000’ on NW slope.~ 32 degrees. We did this 2 times on what we thought to be low angle slopes. ended up skiing down a low angle ridge line. The buried hoar isn’t everywhere but it’s touchy when found.