This is Chris Lundy of the Sawtooth National Forest Avalanche Center with your Backcountry Avalanche Advisory and Weather Forecast for Thursday, January 28, 2010 at 7:30 am. Soldier Mountains We provide the Bottom Line for the Soldier Mountains on Friday, Saturday, and Sundays at 7:30am. Please continue to read the full advisory as the information may be applicable to this region. Primary Avalanche Concern: Many people have been asking me what’s different about this season, and two things stand out: an unusually weak and uniform facet layer and a pattern of slow loading. Early season snow – from the South Valley all the way into the Sawtooths – became extremely weak and cohesionless during cold weather at the start of December. On a normal year, average snowfall would bury the facets more deeply and lead to strengthening through compression of the layer. Instead, meager snowfall has loaded the weak layer very slowly, allowing it to remain intact with very little change since it was first buried. Now a dangerously thick slab has accumulated on top of the facets, and the snowfall that occurred last week has brought us to the edge. A widespread avalanche cycle took place towards the end of last week, and I saw further evidence of this riding out Baker Creek yesterday. Just as impressive as the sheer number of avalanches was where they were occurring. I saw many in dense trees as well as relatively benign looking slopes just above the road. Many crown lines were several hundred feet wide, and in some cases approached a half mile. Early in the storm cycle, Brodie Gulch ripped out wall-to-wall; literally any chunk of snow steeper than 30 degrees ended up at the bottom of the bowl. Fortunately riders over the weekend kept their travel to low angle slopes and enjoyed deep powder in the meadows. In our northern mountains we are faced with a deep slab instability, which is particularly challenging since classic signs of instability may be absent, stability tests may give misleading results, and the whole situation becomes less predictable. Under these conditions, uncertainty runs high and the best way to deal with it is to take a step back and use a conservative approach. Evaluating snowpack stability is always a guilty until proven innocent affair, and to prove innocence in this case you’ll need to hire OJ’s lawyer and I hear he’s pretty spendy. Conditions remain particularly dangerous in the South and Central Valley where the facets are the weakest, and where the most snow fell last week. A hiker in Greenhorn Gulch yesterday afternoon heard a boom, and saw three new avalanches on her hike out. These occurred at low to mid elevations and may have been related to warming temperatures yesterday afternoon. Since the snow arrived last week, it’s been relatively cool and cloudy but that will likely change today. Sunny skies will allow temperatures to warm today, especially at low to mid elevations. Rising temperatures cause the snowpack to creep downhill at a faster rate, which increases the stress on an already maxed weak layer. We may also see some loose snow avalanches on solar aspects, and roof-a-lanches could also become a danger today. Current Conditions: Temperatures yesterday warmed a bit during periods of sunshine, with highs at upper elevations climbing into the mid 20s to near 30 degrees while down low it hit the mid 30s. Ridgeline winds were light from the south shifting to the northwest. Clear skies overnight have brought colder temperatures this morning, and we’re starting out in the mid teens at all elevations. Skiing and riding conditions continue to be excellent on sheltered and shady aspects, however sun crusts are becoming more common on south facing slopes. Mountain Weather Forecast: High pressure building into our region today will bring mostly sunny skies, mild temperatures, and light winds. Expect highs at upper elevations to reach the upper 20s to low 30s, and in the valley it should climb into the mid to upper 30s. An inversion will likely set up tonight, which will result in even warmer temperatures in the mountains tomorrow. Ridgeline winds are forecast to blow lightly today from a variable but generally northwesterly direction.