Vail & Summit County
SnowpackAndrew McWilliams · Nov 11, 2024 · Vail & Summit County
Weather
Clear skies, calm winds, and temperatures just above freezing.
Snowpack
We observed a snowpack that was about 30cm to 80cm deep. The average depth was closer to about 50cm. Slopes on the southern half of the compass were mostly composed of recent storm snow resting on the ground. In a quick pit on a west-facing slope, some weak snow was starting to form near the ground that was overlain by decomposing fragments. The recent snow was not forming a slab in that location, so there wasn't an avalanche concern. Where we descended on southerly slopes, there was no weak snow near the ground and the snowpack was composed of decomposing forms and rounds throughout. Not surprisingly, these slopes had the shallowest snowpack. The warm temperatures and sunny skies the past two days created surface crusts and when we descended in the afternoon the surface snow was becoming moist even in shaded areas. Where we dug on a northeast-facing slope at the upper end of near treeline we found a slab resting on weak snow. There was a one-finger hard slab (on the Hand Hardness Scale) resting on a layer of faceted grains that varied from about 5cm to 20cm thick. In an Extended Column Test (ECT), we got a propagating result after taps from the elbow in two tests. In a Propagation Saw Test (PST), we got propagation to the end of a 100cm column after a cut of 27cm. These results suggest you could trigger an avalanche on slopes where this slab on weak snow structure exists. That said, it seems like this structure is not widely distributed across the terrain. Slopes either lack sufficient coverage, a basal weak layer, or a slab. While you could trigger an avalanche, the places where troubling structure exists are generally not connected and isolated to terrain features at upper elevations on shaded slopes. We did note a few isolated collapses, but they were also confined to small terrain features. Finally, we observed widespread surface hoar development where we traveled with grains reaching over 2cm in length - most were in the 4-8mm range. In some areas, the surface hoar was resting on a crust with small facets below it. This weak surface was continuous across the terrain and we found it on all aspects in the morning. Look for avalanches at this interface if these grains get buried by the next storm.