January 27, 2021
January 28, 2021
Zone or Region:
Did you trigger any avalanches? Yes
Was it intentional? Yes
Size 1: Relatively harmless to people
Easily triggered this 4F hard wind slab just off a ridgeline on the north side of Windy Knob about 200ft below the top. The crown was from 20-35cm deep x 7m wide, and it ran about 50ft downhill before stopping with lower angled slopes below. Wind slabs were isolated to near ridgeline and upper elevation terrain, but substantial drifting had occurred despite the light to moderate winds. This slab ran on weaker storm snow just above faceted grains over a stout crust.
Did you observe any avalanches? Yes
Did you see shooting cracks? No
Did you experience collapsing or whumpfing? Yes, Isolated
I experienced isolated cracking around 5,000ft elevation on open slopes. A closer look revealed the collapsing was occurring on a crust/facet/crust sandwich (beneath a thin crust on a layer of larger facets, above a more stout crust. See profile for details. Cracking and minor collapsing was very isolated, as it felt like there wasn't quite enough snow on it yet to cause larger, concerning collapsing. I've observed this sandwich structure within the zone at various elevations in different places and may make for a lasting weak layer structure as we slowly add more snow over it.
I was able to get results with tilt tests within the new snow 15cm down, and also at the interface of the storm snow and small grained facets above the thin crust. Storm snow was very soft, and uncohesive.