Wide propagating (R5) avalanche across Far East Ridge of Tamarack Peak.

We toured carefully around the avalanche terrain on the Far East Ridge of Tamarack Peak today. Dangerous, unstable conditions were expected and we managed terrain carefully to avoid the avalanche hazard.

Shortly upon departing from the hwy we encountered our first of many shooting cracks, whumpfs, and snowpack collapses of the day. During the largest collapses we could feel the snowpack under our feet drop 1 to 2 inches as the deeper layers of old faceted snow collapsed. Digging out some of the cracks we triggered, we could trace them down to the Dec 11 facet layer found at the old/new snow interface. While there were also storm slab cracks within the upper snowpack and plenty of weak old snow in the lower snowpack, this Dec 11 layer at the old/new snow interface was the weak layer on which the vast majority of avalanche activity and other obvious signs of instability were occurring today.

As we moved along the Far East Ridge and got just west of the GasEx paths, we encountered a fresh natural wind slab avalanche that had failed full path width (R5) and wrapped around one corner. This avalanche is outlined in a separate observation here: https://www.sierraavalanchecenter.org/observation/2021/dec/13/1000/far-e...

This avalanche along with the signs of deeper, persistent instability already encountered gave us a good indication of what to expect once we got over to the main avalanche terrain on the Far East Ridge. No natural avalanche had occurred yet at this spot so I began approaching cautiously along the ridgetop in still sub 30 degree slope angle terrain. I stopped and jumped up and down a few times on my skis in a intentional trigger attempt and was able to trigger an avalanche on N to NE aspect terrain near treeline at 9,200'. This avalanche propagated nearly 900 feet wide, across of entirety of this section of avalanche terrain, wrapping around several corners in the process. We traveled along the ridgetop to the far end of the avalanche where we found the terminus of the cracking in lower angle terrain. We were able to dig out the crack in a safe location and verify that the old near surface facets (Dec 11 layer) at the old/new snow interface was the weak layer for this avalanche. While this avalanche occurred in traditional wind loaded, wind slab terrain, its full path width and beyond wide propagation and failure layer are that of a persistent slab avalanche.

We continued to avoid entering any avalanche terrain and finished our tour- more more whumpfs, cracks, collapses, and enjoyable travel conditions in non-avalanche terrain.