NE facing West monitor on the Park City ridgeline. West Monitor had two different slides, the largest was 80ft wide 12 to 14 inches deep and ran 800ft to the flats. Appeared that a cornice drop was the trigger. Must have occurred at the end of the storm. The bed surface had an inch or so of new snow on top. It also must have sympathetically released, the roll-over skiers right of center, separate slide, but looked like same time frame. One other small pocket released after the storm 20ft wide and ran 3/4 track, also triggered by cornice drop. Both slides ran on facets above a fairly stout crust on the ground.