New snow lies on a snowpack that contains weak persistent snow layers. In addition to being able to trigger surface sloughs or shallow soft slabs in very steep terrain, the chance continues for the weight of a single person to trigger slab avalanches on these older layers above 7500 feet. Late yesterday afternoon, a skier triggered such a slab at the top of Spacewalk, a chute just to the south of the Jackson Hole Mountain Resort. The skier was carried full track, sustained injuries but was not buried. Slab depths were approximately two feet at the top of the chute where it initially failed and three feet at the bottom where a secondary slab released. A fatality occurred on Saturday near Blind Bull when a snowmobiler triggered a small slide. Avalanches at low elevations are unlikely except for in isolated pockets.
Above 7,500 feet, skiers and riders could trigger persistent slab avalanches one to three feet in depth on faceted snow that developed in November and early December. Evaluate the snowpack and terrain carefully and have a safe Christmas day.
( Discussion is generated from the previous day's afternoon forecast. )Periods of flurries or light snow are possible through the night with little accumulation expected. It is looking to be a white Christmas with light snowfall returning during the morning and continuing throughout the day. Temperatures are to rise from near ten degrees to the low twenties. Winds are to vary between the south and west and have averages below fifteen miles per hour. The general avalanche danger will remain Moderate at the mid and upper elevations and Low at the low elevations. The main concern continues to be with the buried weak snow that resides in the snowpack. Slides involving those layers could be triggered by individuals or groups in steep terrain that has been loaded during strong wind events. These slabs could have depths of one to three feet. New snow that fell today and is to fall tomorrow is not a widespread problem but could be initiated in very steep terrain as loose snow sloughs or as very soft slabs in wind loaded areas. Below 7500 feet the snowpack structure is poor however avalanches are not likely except for in isolated areas of very steep terrain.
