Touchy R5 storm slab and wind slab avalanches on Andesite Peak and Castle Rd.

We toured Andesite Peak today looking at the expected storm slab and wind slab avalanche problems. Early on we noted minor storm slab cracking within the new snow along the edges of our skintrack while breaking trail. Once we encountered our first test slope to work with, the widespread instability became apparent. Pretty much any slope over about 35 degrees in slope angle was unstable. We were able to remotely trigger several wind slab and storm slab avalanches from up to 50 feet away in connected low angle terrain off to the side or from the top. Avalanche size was consistently D2 with R5 width. Once a snowpack failure avalanche event was triggered, it would link multiple avalanche paths together with connection cracks across sub 35 degree terrain in between.

At noon we measured just under 2 feet (57 cm) of new snow in wind protected below treeline terrain at 7,900' and it was still snowing 1 to 2 inches per hour (S2 to S5). We identified the weak layer for today's avalanches as needle crystals (3-4mm) and small rimed particles (2mm) located about 4 inches (12 cm) above the old/new snow interface. At this weak layer there was also a subtle density change of 4F+ over 4F hardness within the storm snow.

Moving up into near to above treeline terrain we transitioned from the storm slab zone to the wind slab zone. Here we were again able to intentionally trigger avalanches with very wide propagation of up to 700'. Avalanche behavior was very similar to the storm slabs below treeline, but with locations limited to leeward areas. Again cracks connected across lower angle terrain linking one avalanche to another in the steeper areas.

We descended off of the summit of Andesite Peak avoiding all exposure to avalanche terrain.