Quick report
- Red Flags
- Wind Loading, Poor Snowpack Structure
- Red Flags Comment
- <p>Noted no new avalanches. Wind loading predominated today, with firmly packed snow surface in exposed locations. Noted one shooting crack (2m or so length) on a wind slab on a NE slope around 7800ft. In pits, the surface wind affected snow (1F) was between 5 and 15cm thick and in some cases separated readily from the underlying storm snow just by touching it with the shovel. Difficult to do a formal test on this thin layer as a result, but those bits of data point to still reactive surface wind slabs.</p>
This is a fairly representative pit of the NW to N to NE terrain between 7000 and 8000ft. 40-50cm of basal facets overlaid by right side up 1F to F hard snow, with 5-15cm of 4F to 1F+ wind affected snow on top (hardness varied by location).
Completed 5 ECTs and got scores of ECTN20, ECTN25, ECTX x2, and ECTPV (failed upon isolation). Cracking/propagation occurred just below the interface between the facets and snow above.
For one of the ECTX tests, managed to get propagation with some "bonus taps" from the shoulder with some extra gusto. The other clear difference from the ECTPV and the other pits was the snow depth. HS was 150cm in that pit, compared to 95-115cm in the others. This meant nearly a meter of snow atop the basal facets vs only ~50cm of snow elsewhere. This difference in snow weight or tapping force on the shovel makes me think similar results could be had anywhere the wind has increased the snowpack depth, even if the snow surface doesn't appear too wind affected at the moment.
As noted above, surface wind slab was quite reactive and very poorly bonded to underlying storm snow. In this NW pit at 7700ft, there's a pretty clear void separating the wind slab from the snow below, leading to very easy failures.
Snowpack
Picked up 3-4" of new snow from the Wednesday PM system. Unfortunately, this was wind affected pretty much everywhere. Wind skin was on the snow surface as low as 6000ft, with thicker surface wind slab increasing with elevation and exposure. Variable riding with few soft turns to be had, even with determined sleuthing.