Above 8000 feet, the possibility continues for skiers and riders to trigger slab avalanches involving weak faceted snow that was buried in late November. These slabs may fail after a slope has already been tracked when a particularly weak spot is hit or by larger loads such as groups of skiers or snow machines. Snowpack evaluation may not provide the information needed to determine slope stability, therefore cautious route finding and decision making is essential. Avalanches are unlikely below 7500 feet except in isolated pockets in steep loaded gullies. Yesterday morning a recent, large, natural avalanche was observed on the east face of the Grand Teton at an elevation of 13000 feet (a picture is on the website).
A problematic layer of faceted snow lies throughout the upper elevation snowpack. In some terrain this faceted snow is further complicated by crusts, particularly on solar aspects. The soft slabs that lie over this weakness may fail with depths of one to three feet. New snow will slightly increase the sensitivity of this hazard.
( Discussion is generated from the previous day's afternoon forecast. )Cold air will keep temperatures in the single digits at the upper elevations overnight and highs in the low teens tomorrow. Mild inversions are again expected in the morning at the low elevations, where highs in the mid-twenties are possible in the afternoon. Moisture from a weak disturbance over Utah will provide clouds and the chance for occasional flurries or perhaps an inch or two of accumulation tonight through Monday. The general avalanche danger will be Moderate at the mid and upper elevations. The persistent slab problem involving faceted snow will continue tomorrow and into the foreseeable future. As the snowpack adjusts to recent loading these slabs will slowly decrease in likelihood of triggering, meaning they will be less sensitive. Make no mistake that this does not indicate that slopes are stable. They will simply be harder to predict and may fail after a slope has been tracked several times once a weak spot on the slope is hit or to larger loads such as groups or snow machines. Avalanches at low elevations remain unlikely due to relatively shallow snow depths, and potential activity is limited to wind loaded steep gullies.
