Skied two laps on Two Dogs this afternoon and observed multiple parties in the area. Sometime between lap one and lap two, an avalanche occurred on the north facing slope between Oingo Boingo and Two Dogs (did not see it as it slid). The slide appeared to break right below the cliff band, but I did not get close enough to measure the crown or determine which layer failed. The slide ran approximately 500 feet and covered several tracks from earlier in the day.