40cm hard slab failed above the 3/5 melt-freeze crust, 200' wide
Signs of Unstable Snow
Did you see shooting cracks?
Did you experience collapsing or whumpfing?
Travelled to around 7000' in the Lake Basin environs. Noticed widespread wind affect on all aspects and all elevations. Found solar aspects to hold a stout crust at the surface or 5-10cm down, depending on wind transport. NE/E/SE aspects were guarded by large cornices. We investigated a prior crown that was partially buried and did some hand shears and compression tests both in an area that had slid and one that had not. In both areas, we found sudden planar failures above a stout crust at 40cm depth as well as a faint crust at 45cm depth.
We investigated northern aspects to see if they had more stability but hand shears quickly identified a 5cm soft slab sitting on top of a 25cm hard slab on the same stout crust on that aspect, so we skied mellow slopes <30 degrees.
Observed Avalanche Problem #1:
Compression tests on a SE aspect at 6700' revealed reactive interfaces around melt-freeze crusts at 40 and 45cm depth. Three compression tests were done with results CTE7,CTM11,CTM12. The crust at 40cm depth was stout and likely the 3/5 interface.
Total snow depth 395cm
Rough hardness profile:
45-47cm: K (MFcr)
50cm: K (MFcr)
See video for a test: https://youtu.be/ci8Rk_nnKOI