Heavy, wet snow with snowfall rates of 1in per hour in the AM. Gradual warming throughout the day with precipitation transitioning to a rain/snow mix in PM up to ~5500ft. Light westerly winds with little blowing snow and very minor wind effect near and below treeline.
Dec 20, 2021
Triggered a small slab avalanche (D1) 4-6in deep within new snow on a steep convex roll (6200ft, E aspect). Observed another slab avalanche (unknown trigger) that broke 6-8in+ deep and impressively wide on a steep slope above Hwy 35 (4300ft, E aspect). See photos.
Observed around 30in of new snow above the prominent rain crust buried 12/18. The top 6in+ of new snow were heavy and dense, and sat above less dense storm snow - an obvious upside down layering configuration (4F over F). Inter-storm layers ↓6in and ↓12in produced sudden planar fractures in snowpack tests but no propagation. These moist storm snow layers near the surface were challenging to accurately assess with snowpack tests but recent avalanche activity was bullseye data the snowpack was unstable. Below the top 6in of surface snow, the rest of the storm snow had a favorable hardness profile (F-4F) and was well bonded to the 12/18 crust where I looked in a test pit at 5500ft (see photo). Elevated danger and mediocre skiing aside, this heavy load of dense snow is great base building material and is really helping to fill in rough terrain and creek beds.
Layer Depth/Date: up to 30in deep - storm snow since 12/18
Storm slab with wet characteristics