Reactive buried surface hoar on Andesite Ridge.

Surface hoar (SH) buried around 45 cm or 18 in below the snow surface was observed in this areas and was reactive in snowpit tests. This buried SH was present in open areas at treeline and below treeline. Buried SH was not present above treeline in the more traditional avalanche start zones on NE-E aspects along Andesite Ridge. Recent avalanche activity near and below treeline in this area up through yesterday (Jan 7) is thought to have failed on this weak layer at the base of the recent storm snow, which accumulated since the morning Jan 5. This SH ranged from 3 mm to 10 mm in size and was most reactive in snowpit tests on the NE-E aspects observed. No true N aspects were available for testing. SE aspects were not observed.

Two testpits were dug in addition to the graphed snowpit. One additional testpit dug on a NW aspect, 28 degree slope, at 8080' (39.351591, -120.367267) produced repeatable ECTN results. Some 3 mm SH was observed in the pit 20 cm down, but did not propagate in large column tests. The second additional test pit which was dug on a shaded, open, below treeline, E aspect, 10 degree slope, at 7,460' (39.349322, -120.357910) produced repeatable ECTP-25 Q2 results on 6 mm SH buried 45 cm below the snow surface.

What were once near surface facets at the base of the recent storm snow since Jan 5 are now well rounded with few to no corners visible under 10x magnification.

Surface hoar newly formed last night on the snow surface showed signs that is would likely persist through today in any shaded areas and on NW-N-NE aspects steeper than 20-25 degrees.

Photo 1: Pointing at the faint line of problematic buried SH in the snowpit. Also note the newly formed SH on the snow surface.

Photo 2: Surface hoar grains taken from the weak layer following ECTP results.

Photo 3: Newly formed SH on the snow surface 10 - 15 mm in size.