We observed some disturbing traverse tracks directly underneath some behemoth cornices on the Magnum ridge line. A large piece of cornice appeared to have separated from the ridge line when 1 of the skiers dropped in, but did not release. This is likely the cornice that failed and triggered the slab.
The cornice the tracks cross under just before the tracks descend looks to indeed be the cornice that fell and triggered the slab below later that day/night (Saturday 1/30). The second photo was taken on Sunday 1/31 by Susan Goodwin from the Cornbiscuit Ridge showing the aftermath of the cornice fall.