Avalanche occurred as a result of Dec 26-27 storm event that produced 19" of snow at 2.6" SWE. This is a repeat runner this season. Several other large avalanches were observed in Gold Basin the same day. Failure is assumed to be on a known persistent weak layer of facets 30-40 cms above the ground that formed during the November high pressure. Faint debris is visible in the line of the x's leading me to believe this may have avalanched wider than is noted.