Eastside Region

Avalanches remain unlikely today. Monitor surfaces for warming throughout the day and exercise caution in consequential terrain.

In the next 24 hours, increasing cloud cover may trap heat and increase avalanche hazard. Winds will help keep the surface cool, but cloud cover may reduce the surface freeze tonight, and wet problems may become more likely tomorrow.

While our main concern remains isolated surface instabilities, the ESAC team has also been monitoring what's happening beneath the surface. To see a slab avalanche release, a bed surface, a weak layer, and a slab are all necessary. Across the zone, it is hard to find all three of these ingredients in the same place. Three different pits on North-facing aspects around 9,500' from Bishop to Lee Vining illustrate this well.

• In the southern portion, weak, faceted grains sit above the New Year's crust. Facets dominate the upper snowpack, and there is no strong slab. South of Mammoth, there is a bed surface, a weak layer, and no slab.
• In the Mammoth to June area, the New Year's crust has minimal weak, faceted snow above and below, and instead holds three feet of stiff, rounded grains overtop. Weak facets are developing near the surface. In the Mammoth area, there is a bed surface and a slab, but no weak layer.
• In the Lee Vining Canyon area, weak, faceted snow lies above the New Year's crust, and a wind-drifted slab rests on these weak grains. This old wind-drifted slab is weak and faceted near the surface, but it is still strong enough to fail in stability tests. In this isolated pocket, a slab, a weak layer, and a bed surface are all present. 

While there are isolated areas with the ingredients for a slab avalanche, it remains unlikely that a human could trigger one. Our structure is not a problem now, and significant new snowfall may be required to overload buried weak layers. The ESAC team will continue to monitor this poor structure as we move forward. In the meantime, it's a good time to get after it and explore the range.