These observations cover our three field days this last weekend while we were teaching a Level I course in the Mt Troy area. Conditions changed little over the three days, except for ongoing faceting and surface hoar growth, though it is snowing lightly as we post these observations on Monday morning. There is no wind and less than 10 cm total accumulation, so there is little load. But NE winds forecast for the afternoon can be expected to produce some unstable windslabs over facets and buried surface hoar.

The profile from Saturday is quite typical of what we saw throughout the course in sheltered areas. In the wind exposed areas, the snow was either blown right down to the crust from the December 23-24 thaw or there were localized sensitive windslabs. A few other areas had a shallow layer of faceted grains over the thaw crust.

Our test results were spatially variable, but all tests fractured in the loose sugary facets just beneath the 145 to 146 cm crust. We traced the spatial variability in part to the runnels (grooves) that formed in the crust. These are the surface expression of zones of enhanced percolation beneath them during thaw periods, and we found many refrozen percolation columns and zones beneath the runnels that connected the 145 to 146 cm crust to the 120 cm crust from the December 23 to 24 thaw. Where there were no percolation structures supporting the upper layers, shear values in the loose facets were much weaker.

There were no signs of instability except for shooting cracks and mini-slabs in the fresher windslab areas. Those we found were all small and thin, but thicker or more extensive windslabs should be avoided. Where there were no windslabs, slab tests had a relatively low energy score of 4, meaning that the slab crumbled irregularly over less than half the area we undermined.

In areas sheltered from wind, the thin crust from the drizzle on Wednesday the 8th has weakened under the influence of the faceting process and now allows reasonably smooth turning.

The well developed surface hoar and near surface facets interlayered with and resting on melt freeze crusts are likely to produce an avalanche cycle on the next big loading event. Size and timing will depend on how the load arrives. If the load arrives quickly, paths will run early and small. If it arrives gradually, they will run late and big. If a gentle gradual thaw comes or if the loading rate and amount are small, nothing will happen.