This small avalanche happened naturally overnight in a location I'd not seen before, perhaps 100ft below the skin track on a convexity. It failed on the old surface--now wet--facets atop the subsurface crust. The crown was about 10 inches of wet storm snow, with a few inches of additional new snow atop the bed surface when we saw it this morning (thereby indicating the overnight timing). Given the moisture content of both the slab and the facets, wet slab seemed most appropriate.