A snowmobiler who triggered a large slab avalanche in the Breccia Cliffs area near Togwotee Pass yesterday afternoon did not survive. Very large, persistent slab avalanches could be triggered in steep terrain, especially by larger triggers like snowmachines. The consequences of triggering one of these dangerous avalanches are likely to be severe. Dense wind slabs could also be triggered by humans in steep avalanche starting zones. Avalanches are unlikely below and elevation of 7,500 feet except on isolated terrain features during the warmest portion of the day. As the day progresses, sunshine and warming temperatures could increase the sensitivity of areas of unstable snow to human triggers at all elevations. Conduct snow stability assessments, monitor conditions and avoid steep terrain in areas where the snow structure is poor.
Dense wind slabs could be triggered by skiers and riders in very steep, avalanche prone terrain above an elevation of 7,500 feet. These slabs, with depths to two feet, could become more susceptible to human triggers as the day warms.
Areas with poor snowpack structure exist and the weight of a single person is still sufficient to trigger a deep persistent slab avalanche in these areas. Large triggers, such as snowmobiles, the release of a wind slab or a cornice failure, are more likely than an individual skier to trigger one of these deadly avalanches. Slab depths are likely to vary from three to six feet at the higher elevations and one to three feet at the lower elevations.
( Discussion is generated from the previous day's afternoon forecast. )Conditions will remain dry overnight. Clouds will increase on Tuesday. Skies are expected to be overcast by the end of the day. Temperatures will drop to zero or below overnight and rise into the teens and 20s during the day. Winds will be light and variable. The general avalanche hazard is forecast to be moderate above an elevation of 7,500 feet. Humans who venture into steep avalanche starting zones could trigger dense wind slab avalanches 1 to 3 feet deep. Deep persistent slabs avalanche are still a concern, especially in the Togwotee Pass area and other areas that still exhibit poor snowpack structure. These dangerous slabs could be three to six feet deep and are more likely to be initiated by larger triggers like snowmachines, cornice drops or the release of a wind slab. At the lower elevations the general avalanche hazard is expected to be low. Avalanches are unlikely except on isolated terrain features during the warmest portion of the day. As the day progresses, sunshine and warming temperatures could increase the sensitivity of areas of unstable snow to human triggers at all elevations. Conduct snow stability assessments, monitor conditions and avoid steep terrain with poor snow structure.
