Dangerous avalanche conditions exist. A series of storm systems has brought periodic snowfall to the area since Tuesday. During this time, over two feet of snow has fallen in the Southwest Trails Area, with greatest amounts in the Salt River Range. Winds that have been strong at times have varied from the south-southeast to the northwest. Caution is advised as the new and recently fallen snow could be easily triggered as soft slabs in steep leeward terrain by backcountry enthusiasts. Once triggered, such an event could cause deeper instabilities in the snowpack to fail, resulting in large to very large avalanches. The size and sensitivity of triggering these avalanche events is greatest at the mid and upper elevations, however human triggered low elevation slides remain possible.
Skiers and riders could trigger recently formed slabs in steep wind loaded terrain. These slabs could fail on density breaks within the last few days snowfall or on hard sun crusts or faceted snow that was buried on Tuesday with depths to thirty inches at the higher elevations and to eighteen inches at the lower elevations.
During the last several days, over two inches of snow water equivalent has been added to a snowpack that has buried persistent weak layers. Above 7,500 feet, this load has increased the likelihood of these weaknesses failing to human traffic, or more likely, following the release of a wind slab. Once triggered, these slabs could have depths of two to four feet. The snowpack is comprised of mostly faceted snow below 7,500 feet, where skiers and riders could trigger recently fallen snow that could also be considered a persistent slab with depths to eighteen inches.
( Discussion is generated from the previous day's afternoon forecast. )The next system is to impact the area this evening and tonight. This could bring another seven or eight inches to the upper elevations of the Tetons by morning with the outlying areas and lower elevations receiving approximately five inches. Lingering snow showers will bring more accumulation and are expected to taper off through the day on Monday. Temperatures are to be cooler, with the mountains having highs in the low twenties. Southwest winds will be strongest during the snowfall with averages between twenty and thirty miles per hour. The general avalanche hazard is expected to be Considerable tomorrow. New snow will form new surface instabilities and could combine with the recently fallen snow to depths that could reach thirty inches in steep leeward terrain. These slabs could be triggered by a single person and could also release deeper weaknesses in the snowpack to depths to four feet at the higher elevations or to two feet at the lower elevations. Backcountry skiers and riders should exercise caution during this time of sensitive, dangerous conditions and elevated avalanche danger.
