Dense early season storms in November deposited enough snow for good coverage, however generally dry conditions since then have left the snowpack in the Sierra thin and snowline is around ~9,000 to 9,500’ around Mammoth, and higher elsewhere. Recent high pressure and mild daytime temperatures have slowly edged snowline higher with only patchy coverage below. Early season conditions exist with many obstacles hiding just under the snow surface.
A mild disturbance to the Northeast brought snow and wintry conditions to the Sierra on December 16th depositing small wind slabs on West-South-East aspects. Prior to that last shot of weather, moderate to strong temperature gradients in the snowpack formed during the high pressure period (roughly the first two weeks of December) weakening the upper snowpack. Layers of in-cohesive, sugary snow have been observed between denser layers of old wind deposit or in combination with the melt-freeze crust that was buried on November 27th. Most of the upper snowpack consists of these facet grains in one form or another. The snowpack near and above treeline alternates between soft facets in sheltered areas, wind stripped, wind deposited areas, and melt/freeze patches. Near and below treeline, surface facets have provided some good skiing in sheltered areas, but warm temperatures have made things sticky and spring-like on sun exposed aspects up to ~10,000’. As the next storm passes through early Wednesday morning, the facets in the upper snowpack may form a weak layer once buried, and the melt-freeze crusts may act as a prime bed surface for future avalanches. Be wary of hollow sounding snow, and cracks shooting out from your feet. Observe wind loading patterns paying special attention to leeward slopes, gullies, and depressions. Below ~9,500’, natural and triggered releases are unlikely due to little or no snow.
