Northern San Juan
AvalancheAmy Pertuz · Dec 14, 2018 · Northern San Juan
Weather
Clear, crisp, and breezy in the alpine. Ridgetop winds were still transporting snow onto Easterly and Southerly aspects
Snowpack
HN24 of 12" redistributed by many-directional winds, but predominately NW'ly winds. Due North, Northwest slopes were strafed by NW'ly winds, as were some W'ly aspects ATL. BTL, E and SE had most significant new snow loading. On SW-SE slopes this new snow fell on a thin suncrust from 12.07 which now has associated facets on either side of crust. Columns failed on isolation on this interface between storm snow and old facet crust combo in both SW BTL and SE BTL hand shear tests (14" down). This interface was otherwise not reactive to tests of ski pressure. E aspects BTL did not have this defined suncrust, but did have a prominent older interface below the new snow which was also a crust-facet combo. This layer (13" down) produced failures but no propagation in tests. NE aspect BTL had some of the worst snowpack structure, with new snow sitting on small near-surface faceted layer (11" down) but this aspect was unreactive to tests. A pit dug in Swamp Angel NE BTL on Weds similarly also had poor structure but no propagation on the large facets (20" down,), and hard failures, if at all, in compression. Experienced localized collapsing to 60 ft on E aspect BTL (Commodore) and to 40 ft NE aspect BTL (Swamp), but no other cracks, whumphs, or signs of instabililty. Surface snow BTL was thickened by wind deposition, but still soft surface conditions.
Avalanche
Numerous slabs visible on RMP but the continuing activity of E-NE slopes near and above TL with impressive propagation continues to be the most noteworthy.