Very dangerous avalanche conditions exist. New snow and strong southwesterly winds have added load to a snowpack that has buried weak layers. Additional snowfall and strong winds that are to veer to the northwest during the day will further stress these weaknesses. Travel in avalanche terrain is not recommended as natural avalanche activity is likely and human triggered avalanches are very likely. Avalanches could occur in the form of wind slabs at higher elevations or as persistent slabs at all elevations, involving older weak snow that lies close to the ground.
New and recent snow could be triggered as wind slabs in steep terrain above 8000. These sensitive soft slabs were formed during southwest to west winds over the last three days and could have depths to two feet. Changing wind direction will continue to load and increase the sensitivity of these slabs even as snowfall diminishes this afternoon.
Persistent weak layers of faceted snow exist throughout the backcountry. Above 9000 feet, if one of the these persistent slabs is triggered, it is likely to be in the form of a very large hard slab with depths of three to five feet. They could be more sensitive between 7500 and 9000 feet, where they could be hard or soft and have depths of two to four feet. At the low elevations the structure of the snowpack is very poor. At these elevations, slabs will be sensitive and are likely to involve faceted snow to the ground. The sensitivity of these slabs will also increase as additional snowfall and strong winds further load avalanche starting zones.
( Discussion is generated from the previous day's afternoon forecast. )A Winter Weather Advisory has been issued by the National Weather Service. It is effective until 3pm Tuesday. Snow is expected with the heaviest snowfall to occur between 7 pm this evening and 3 am Tuesday. Approximately 10 inches of snow and nearly an inch of moisture is expected overnight. Winds are to increase to averages of 25 to 40 miles per hour and become westerly Tuesday morning. Snow is to diminish Tuesday morning as winds lessen and become northwesterly. Mountain temperatures are to rise from the low teens to the twenties. The general avalanche danger in the Teton and Southwest trails areas could increase to HIGH if both significant snowfall and strong winds occur. In the Togwotee pass area, the danger is likely to increase to Considerable. Wind slabs involving the new storm snow and possibly recent snow could be human triggered with depths to two feet in steep freshly loaded terrain. The primary focus and reason for conservative decision making involves buried persistent weak layers of faceted snow. Failure of these layers could result in very large avalanches at higher elevations or widespread smaller avalanches at lower elevations. Under these conditions, collapses in the snowpack could remotely trigger slides. Be sure to avoid being under suspect slopes.
