Witness a powder cloud below the Hallway around 1 pm from the top of 2 trees. Could make out a crown high on the slope above the cliffs which was 2-2.5' deep and a second crown ~4' down below on the apron. Few minutes later watched 2 skiers descending. Unsure if they remote triggered this slide or triggered while skiing. Between the two crowns I assume the avalanche was 1500' vertical and likely ran from the top of the ridge to the valley below.