Since the dry period ended on December 11th, the upper elevations of the Tetons have received approximately four feet of snow containing nearly 5 inches of moisture. Yesterday's storm started warm, ended cold and was accompanied by very strong winds that veered from the southwest to the northwest. Wind slabs could fail on density changes within the recent snow however the focus for safe backcountry travel needs to involve evaluation of the persistent slab problem which lies at the interface between the dry period and the recent snow. Skiers and riders have the potential to trigger slides involving these layers at all elevations but particularly above 7500 feet where they could be large.
Faceted snow and melt-freeze crusts formed during an extended dry period that ended on December 11th. Slabs above that layer could be triggered today. These slabs could be soft or hard with depths to three feet at the higher elevations and to eighteen inches at the low elevations. Be particularly wary of unsupported slopes and cliff areas.
Dry weather will continue tomorrow with mostly clear skies and a valley inversion. In the mountains, temperatures are expected to start in the single digits and then warm into the twenties, while in the valleys temperatures should start below zero and then also warm into the twenties. Northwesterly winds are expected to be light at 10 to 20 miles per hour. In the Southwest Trails/Grey’s River and Teton forecast areas, the general avalanche hazard is expected to remain Considerable above 7,500 feet. In these areas, persistent slab avalanches are likely to be triggered by skiers and riders on steep avalanche-prone terrain. Buried weak layers vary in distribution and in some areas may be stubborn, but where this structure exists dangerous avalanche conditions could be encountered. These problem layers could be hard to detect without checking the snowpack structure. In the Continental Divide/Togwotee Pass forecast area, where there was less snowfall since December 11, the general avalanche hazard is expected to be Moderate. It remains possible for skiers and riders to trigger persistent slab avalanches one to two feet deep. In all the forecast areas, below 7,500 feet the general avalanche hazard is Low. At these lower elevations, there is only one to two feet of snow, which has experienced above freezing temperatures for over 24 hours, and avalanches are unlikely except for isolated pockets of deeper snowpack on steep slopes.
