Quick report
- Red Flags
- Recent Avalanches, Wind Loading, Collapsing, Poor Snowpack Structure
- Red Flags Comment
- <p>Despite jumping around on lots of suspect slopes, got relatively few collapses today. But the poor snowpack structure dominates conservative decision making in avalanche terrain. </p>
Less-reactive snowpack today, and was surprised given the recent strong winds and quick load of ~0.50" of water weight. Fewer collapses and could not get one ECT to propagate. But am focusing more on the poor structure than on any evidence of increasing stability and am continuing to avoid being on, underneath, or adjacent to slopes steeper than 30°. There is a well-connected slab on top of very weak snow underneath, and all we have to do is get a fracture on one part of the slope for it to all release.
Photo of plumes from NW winds along upper elevation ridgelines, and video of wind-drifting and cross-loading in Scott's Bowl along Park City ridgeline.
High or Considerable danger? I had looked through the same data this morning as Trent did in his forecast, and agreed with his morning forecast of a High danger at the upper elevations. After my tour today ("backcasting") I felt the danger was Considerable, and not High. But it has little difference: I continue to avoid avalanche terrain.
Snowpack
- Instability Comment
- <p>Some incredibly weak snow underneath recent storm slabs from 10,420' north and west along the Park City ridgeline. Depth-hoar, and near-surface facets. Dug several pits today, and all were ECTN with Q2/Q3 results. On a north aspect at 10,000' with ECTN results, performed Propagation Saw Test and got the full 100 cm column to fracture on the buried layer of near-surface facets from November/December (Drew's NFL layer) that was down 30 cms on this slope. This is indicative there is a cohesive slab on top of this weak layer. PST 25/100 End down 30 cms.</p> <p> </p>
15-20 cms very-low-density new storm snow. Some fresh drifts noted both along the ridges and down off of ridges, however, they were not sensitive. Very likely that drifts from very strong SW/W winds were covered by the fresh snowfall.
Was finding rime crust from Sunday afternoon present on predominantly west aspects, with facets and preserved stellars underneath. (Mark Staples was also noticing these same weaknesses underneath the crust in LCC.) Widespread temperature crust on most every aspect as well. Storm snow seems well-bonded to crust, but will keep facets underneath the crust in mind going forward.
On some north-facing slopes > ~9500' was not finding a crust, but preserved near-surface facets from cold and clear temperatures this past Saturday into Sunday, down 15-20 cms. Was able to get clean shears on this layer with shovel-tilt test.