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 at the mid and high elevations. 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. Similar events could happen today. 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.
Periods of light snow are to continue tonight and decrease by sunrise. Lingering snow showers are possible on Wednesday with dry conditions expected for the remainder of the day and night. Temperatures are to rise from the single digits to the teens at upper elevations and into the twenties at the low elevations. Winds are to be light and variable. The general avalanche danger will be Moderate above 7500 feet and low below that elevation. The persistent slab problem continues to exist and the potential for a single rider or skier to trigger slabs of one to three feet involving old snow layers remains. Although the weak layers are relatively widespread throughout upper elevation terrain, determining which terrain features are unstable to backcountry travelers is very difficult. Below 7500 feet, avalanches remain unlikely, except for is small isolated pockets of instability.
