Another deep hard slab was remotely triggered yesterday outside the southern boundary of the Grand Targhee Resort. This slide, with crown depths up to 10 feet, occurred on a south-facing aspect at 9,700 feet. Numerous shallow wind slabs were also easily triggered yesterday. Similar slides are possible today, and once weak crusts breakdown, wet slides could occur at the lower elevations. Any extended periods of sunshine will increase the likelihood of these avalanche problems.
Strong westerly ridgetop winds have created dense wind slabs in exposed terrain at the mid and upper elevations. Skiers and riders could trigger these slabs to depths of one to three feet. These slabs could step down to persistent weak layers deeper within the snowpack.
Near-freezing overnight temperatures, along with latent heat in the snowpack, will keep wet slides possible at the lower elevations once snow surfaces soften.
Dense snowfall has added load to persistent weak layers formed during drought periods earlier in the season. Three different events have occurred over the last couple of days with two of them being remotely triggered. If triggered, these slabs could have depths up to eight feet.
The next storm system will begin to impact the region tonight and continue through Thursday. Up to a foot of new snow is possible by Thursday night. Southwesterly to westerly ridgetop winds at 25 to 35 miles per hour will accompany this snowfall. Overnight lows in the mountains will be in the mid 20s before rising to near freezing during the day. Valley temperatures could dip below freezing during the night before rising into the low 40s, and rain at the lower elevations is likely.Similar slides to today's events are likely on Thursday, and the general avalanche hazard is expected to be CONSIDERABLE. Deep persistent slabs, with depths up to eight feet, could also be triggered by skiers and riders, or step down from the failure of surface slabs. New snow and strong westerly ridgetop winds will increase the likelihood of triggering these slabs. These conditions mandate a conservative approach to terrain choices. The potential for one or more fatalities is very real, and possibly imminent. With overnight temperatures near freezing and valley rain in the forecast, wet slides will remain possible at the lower elevations.
