Investigating the Avalanche on Schallenberger Ridge

Today we headed to Schallenberger Ridge to look at one of the avalanches that failed late on Tuesday. A party of skiers reported this slide to us yesterday. We confirmed it with the local railroad avalanche forecasters, who said it happened Tuesday night (2/28/2023). We also wanted to see what surface conditions look like leading into the next storm. 

As for surface conditions, we experienced soft and unconsolidated snow on steeper shady N aspects and breakable melt-freeze crusts on any sun-exposed slopes. Snow that had fallen off trees also created irregular surfaces in tree-covered areas. The E-SE-S-SW aspects had a thicker but still breakable crust, with soft snow below the crust. Low-angle NW-N-NE facing slopes held a thin, fragile crust. We dug into the snowpack and found that the recent storm snow had strengthened and consolidated. The more problematic layers begin below the thick layer of recent storm snow. 

When we arrived at the avalanche, we located a 4-5+ ft. deep crown and fractures across about 1000 ft. of the slope. We had not seen any signs of lingering instability but still approached it from a low-angle spot without much snow remaining above the crown. We determined it failed when the storm snow overloaded a thin layer of weak snow below a melt-freeze crust at the base of the recent snow (Feb 21 weak layer). We tested this layer today and found that the strong snow above this layer protects it. It would take a large trigger or load, like another big storm, to possibly break this layer. Tests indicated that fractures could still travel along this layer and produce large avalanches if it does break. Looking out from the summit we could see additional avalanches on Anderson Peak and on Trestle Peak.