Quick report
- Cracking
- widespread
We saw many reasons to me more concerned than we expected heading into our camp, which changed our mood and goals for our time out. Primarily the high distribution of sensitive wind slabs, combined with the large amounts of visible transport throughout the whole basin. While the wind was strong enough to sublimate, harden, or strip many high-elevation surfaces, getting to them to find out was the concern. On the 10th we noted much more soft snow than expected as soon as we reached the south side of Sabrina. There was approximately 10cm of F hard snow in the trees with little to no wind effect. This continued, though variable, until we reached 10,300 where the wind had transported harder slabs. On the 11th, we toured higher where we triggered several wind slabs that were slightly larger (D1 - D1-). On most north to northeast slopes, still 4-8cm of PP & DF (0.5) buried underneath the new wind slab, with visible dendrite structures intact. We then approached the north ridge of Mount Tom Ross, hoping to ski the south face. We found some thin sun crust that was variably softening due to the wind. There were some natural avalanches on the south faces where wind-drifted snow had warmed near rocks. We were eventually able to find some highly protected snow due to some tight terrain features. On the 12th, the new snow was very sensitive anywhere the wind had increased the cohesion, or the slopes were steep enough to slide. The sun was aiding cohesion in some places making propagation easier.
Weather
On the 10th, Temp was steady, warming slightly above freezing with SW winds of Moderate to Strong, possibly Extreme at higher elevations, Clouds went from OVC to FEW. Nighttime temps at out camp @10,500' was around -14c and clear. The following day had decreasing winds from Strong to Moderate, Temps rising to slightly above freezing with periods of Light to Calm wind, Sky was CLR. The following day we awoke to a brief period of S5 Snowfall, Strong wind, and obscured sky. Snowfall rate decreased to S-1 as we exited the basin, and temps seemed above freezing below 9500'.
Snowpack
Snowpack measurements were around 60-90cm at 9,000', and increased to 120-160cm at 10,000'. NE slopes above 10,500' had 150cm or more, and we found spots with more than 300cm in multiple aspects (though typically steeper slopes). The snowpack was mostly strong below the surface instabilities though we did not dig to check for the persistent grains specifically. I did dig to the dirt and did not see large crystals near 10,000' NE though we did not do any proper crystal ID at that time.
Avalanche
- Size
- D1 R1
- Type
- SS
- Count
- 2
- Aspect
- S
- Trigger
- N
- Elevation
- 12200 ft
Crown and resulting debris were visible where small terrain features created wind slabs. The debris looked wet which supports the story that the sun warmed the new snow and it failed on the older surface. I unfortunately failed to take a good photo of the debris piles,