Quick report
- Cracking
- specific
We observed wind loaded N and NE aspects near and above tree line. With terrain specific triggers (unsupported slopes), on slopes that reflected terrain more similar to that found above tree line. We observed shooting cracks above an unsupported N/NE aspect, and a small wind slab avalanche. This wind slab measured anywhere from 2-4 inches in depth as a relatively firm and cohesive layer, sitting atop a layer of loose, sugary snow, then freeze thaw crust. Upon arriving to Tam we observed recent avalanche debris paths near tree line on NE and E aspects, slightly obscured by new wind deposited snow. We counted 1 or 2 of these upon arriving from where we were situated near the yurts. We observed no signs of snow instability below tree line or near tree line until venturing onto an aspect and terrain feature that was more reminiscent of terrain found above tree line. This slope also presented with a convexity near the top that bowled out into a funnel/concavity near the bottom third of the slope. We set a skin track on a more supported aspect of the same slope with minimal signs of instability until directly above the convexity. From here, our skin track alone propagated shooting cracks along the length of the aspect that resided directly above the concavity/unsupported slope. We had predicted that this aspect could show signs of instability due to our observed wind loading and wind slab, paired with the terrain feature. Further digging above the convex trigger further confirmed our findings with a 2-4 inch wind slab on top of loose, sugary snow, collectively sitting atop a 1 inch freeze thaw crust.
Weather
- Air Temp
- 21
- Cloud Cover
- overcast
- Wind Loading
- moderate
- Recent Snowfall
- Negligible, all wind transported
- Snow Avail For Transport
- small smounts
Temps remained in the 20s throughout the day. Mild to moderate winds with sustained wind speeds of roughly 5-10 mph, gusts near 25 mph. Overcast skies with high ceiling, although further West the mountains where completely engulfed.
Snowpack
We did not end up digging a pit, but did dig down some to investigate snowpack that the wind slab broke on. It broke on loose, sugary snow that was sitting atop a 1 inch crust from the last freeze thaw cycle we had earlier this week.
Avalanche
- Size
- D1 R1
- Aspect
- NE
- Trigger
- AS
- Elevation
- 7235 ft
Wary of a concave feature on a wind loaded slope, my ski partner and I skinned up a more mellow, and supported aspect before traversing above a convexity on a less supported aspect of the same slope. We observed shooting cracks near this convexity, and the wind slab released, funneling into the concave terrain feature about 2/3rds of the way down this aspect of the slope. Wind slab varied between 2-4 inches. Shooting cracks span about 30 feet.