This avalanche appears to have been triggered by a large cornice fall from the ridge line just a west of East Bowl Pass. The cornice fall probably occurred between 11:45 and 12:45, which was the time between our 1st and 2nd ascent from the bottom Flanagan's. We searched the debris field with our beacons and got no signal. As far as we know this was a natural cornice fall. A motor home-sized piece of the cornice was carried intact more than 500 feet down slope. Several 6-8" diameter trees were snapped in half.