The snowpack in the Sierra remains thin and coverage is limited to elevations above ~9,000 to 9,500’ around Mammoth, and higher elsewhere. Recent high pressure and mild daytime temperatures have slowly edged snowline higher. Early season conditions exist with many obstacles hiding just under the snow surface.
A fast moving low pressure system passed to the north of us on December 3rd accompanied by moderate to strong Westerly winds leaving wind slabs in favored locations on North-Easterly mid and upper elevation slopes. A period of East winds followed that storm and transported snow again across ridgelines and into West-facing chutes and gullies. Since that time we have been stuck under the Ridiculously Resilient Ridge with cold nights and calm dry weather. Strong temperature gradients in the snowpack quickly weakened the snow underneath those wind slabs. Two main faceted layers (layers of in-cohesive, sugary snow) have been observed. One can be found between 5 and 20cm down in the snowpack under the most recent, hard wind-deposits. The second has been observed between 35 and 45cm down in combination with the melt-freeze crust that was buried on November 27th. This observation from last Wednesday highlights the type of problem that may persist in specific locations. That same day, skiers triggered an avalanche while ski cutting near Deadman Pass. More recent observations around the Mammoth Area have shown slab layers to be less reactive during snowpack stress tests. But with limited data I am unconvinced that things have stabilized everywhere. Be wary of hollow sounding snow, and cracks shooting out from your feet. Do some extra investigation to see what the snowpack looks like before committing to your terrain choice. Below ~9,500’, natural and triggered releases are unlikely due to little or no snow.