Below rock bands, so likely started as a point release and entrained dry snow into a large terrain trap. Ran during 18 Feb 2021 storm/wind event.
Signs of Unstable Snow
Did you see shooting cracks?
Did you experience collapsing or whumpfing?
Last week's mix of storms, west and east winds, and high pressure has created a heterogeneous snowpack in the lowlands with diverse travel conditions. Subtle changes in aspect reflect sun's increasing intensity and multiple wind directions this week. Surface hoar buried above sun crust on any southerly tilt and on density change everywhere else.
Sunday's rain at BTL in this area will void much of this.
Observed Avalanche Problem #1:
Cross-loaded slopes from east winds during 17-18 February and strong west winds with moderate transport morning of 19 February 2021. Slabs to 45 cm cracking to 3m. Multiple collapses on SE and E
Observed Avalanche Problem #2:
Wednesday 17 Feb sun crust has surface hoar weak layer buried above it (18 Feb) at all elevations on exposed slopes.