Gunnison

Numerous hard slab avalanches ran during the past few days of northerly winds, averaging D1.5 in size. These were concentrated on the southern half of the compass above treeline. The one crown that we investigated was about 3 feet deep and failed on old, faceted crusts.

A clear sky in the morning gave way to high, thin clouds in the afternoon. Calm to light winds. cloud cover: broken; wind loading: previous; recent snowfall (cm): 0; snow avail for transport: none

Below 10,500ft the snowpack lacked much layering in this area. By the time we reached 10,800, there was some very soft slab development and a layered snowpack. An easterly facing slope at 11,000ft had a 70cm snowpack with about a 45cm soft slab above the December Dryspell Layer. Those soft slabs struggled to propagate far across the slope, in part because of the snowpack variability from past weather events. Another few hundred feet higher, the extra wind-loading and wind hardening of those slabs (still about 45 cm) made triggering an avalanche feel more likely with a couple of larger collapses, but the snowpack structure was still variable across slopes. In the alpine, snow surfaces are often heavly wind effected. Many slopes are wind-eroded, while concave slopes and some lee terrain features have thick, hard slabs. We investigated one avalanche that failed on a south-facing slope at 12,200ft. Here, the northerly wind event had loaded the slope, with the avalanche failing in small facets between the 1/1 and  1/5 crusts.  The bedsurface of the avalanche was the thicker Christmas Crust. . On Easterly to Northeasterly terrain features, shooting cracks and collapsing started to occur around 10,800ft and up to about 11,800, after which the snowpack became more heavily affected by recent winds, with a mix of eroded features and hard slabs that were quiet underfoot.