New snow, drifting snow, and unreactive surface hoar on Silver Peak

We toured on Silver Peak today to look at drifting snow, wind slab development, and to test buried surface hoar. Off and on light snow showers started mid morning with sustained snowfall up to rate S1 from about 10:15 am through our departure from the area at 1:15 pm. New snow accumulation during this time approached 1 inch.

Moderate amounts of blowing and drifting snow were observed along the ridgetops throughout our tour, including earlier in the morning in between periods of snow showers. Drifting snow was being dispersed fairly far downslope, limiting the depth of wind slab development. In this area we noted deeper wind loading onto NE aspects than on N aspects, but no more than 2 inches worth of wind loading were observed anywhere in this terrain at midday.

We tested the Jan 29 buried surface hoar (SH) layer with a loaded PST. Since the SH layer was just 2 to 3 inches below the snow surface and lacking much in the way of a slab on top of it, we follow the the Birkeland, et al. method to build an artificial slab of snow to simulate new snow loading. We selected an open area below treeline with 5 to 8 mm buried SH (noted lat/long, N aspect at 7,540') and added 10 cm of disaggregated snow on top of the snow surface. This added snow was allowed to sinter for 1 hour. During this time it formed into a 1F hard slab on top of the snow surface. We then conducted at PST on the Jan 29 SH layer. Our results (PST 45/100 arr) suggested that propagation along this weak layer would not occur easily. The SH in this location was well bonded to the snowpack layers above and below with no failure in shovel tap/tilt test, so this PST result made sense