Eastside Region

Triggering a sizeable avalanche is unlikely. Expect variable surface conditions and generally thin coverage. Obstacles, like rocks, logs, and brush abound -  use caution. 

Though avalanche activity is unlikely, small and isolated instabilities can be found on shady slopes where weak snow sits under settled slabs, or on sunny terrain where the snowpack gets wet midday.

Snow cover varies across the forecast area. The deepest snow is in the Mammoth area. Coverage is thinner north towards Virginia Lakes and south towards Bishop. North and east-facing slopes between 9,000 and 10,500 ft. have the most uniform coverage. Westerly slopes have unevenly distributed hard wind drifts. Solar slopes have been thawing and refreezing into a crust under sunny skies. High elevations that saw the most winds during the November storms have broken and bony patches of snow.

Before the November storms, a thin and sporadic layer of snow faceted on northerly slopes. You can find weak, sugary snow near the ground above about 9,000 feet on these shady aspects. North of Mammoth, where coverage is currently thin, the facets are large and loose. The last direct sign of instability - a small collapse - occurred in Virginia Lakes on 11/29. Under the deeper snowpack in the central part of the forecast area, these grains have been rounding and shown no signs of instability. They’re harder to find south of Mammoth, where there was less snow before mid-November. Because the layer is so thin, it is often broken up by rough ground, like brush or tallus. Because the overlying snowpack is uneven, areas with a slab over the weak layer are also limited. We have been tracking this layer, and a few snowpack tests performed on smooth ground near Tioga Pass show that, if all the stars align, the facets could propagate across a slope. They’re worth noting if you want to travel on steep northerly terrain.

The last reported slab avalanche was on November 27th, just after the last snowfall. Small wet loose avalanches ran on sunny slopes on the weekend of the 30th.