Wind Slabs and Faceted Snow Under Blue Crag

Submission Info
Wednesday, December 6, 2017 - 12:15pm
Red Flags: 
37° 34' 9.48" N, 118° 58' 46.56" W
Snowpit Observations
More detailed information about the snowpack: 

Toured up above Emerald Lake and Sky Meadow to just N of Blue Crag. Snowpack is faceting with the cold night time temperatures and low sun angle. Below about 10,000' in the trees most layers have become facets except for the melt-freeze crust buried on 11/27. Some shallow (<5cm) soft wind slabs and localized cracking below that elevation. Above treeline, or about 10,000', most snow surfaces were wind affected. Stopped on a NW facing, 24 degree slope at 10,500' when the snow began to sound hollow under my feet. Dug down to perform some snowpack tests. CTV X2 down 10cm on 4F hard facets under P hard wind slab. CT14 SC X2 down 25cm on another, thinner, facet layer under the old surface that was buried on 12/3. Performed two PSTs to test both problem layers. First PST SF 27/100 in the 25cm deep layer, PST End 90/100 in the same layer, PST End 75/100 in the 10cm deep layer. These results suggest that there are two persistent weak layers in which a fracture can easily be initiated, but do not indicate that that fracture can easily propagate across a slope. However, a second PST failed to the end in the 10cm deep layer as I was isolating the column. So it seems that there may be some possibility of propagation. See attached picture and video.

Skiing down above treeline was breakable wind board. Skiing in the sheltered trees, below the wind slab problem, was recycled powder and pretty good. I did kick off one small (3x5ft. and 5cm deep) wind slab in a steep gully just below treeline (see photo other photo).

Only light NE winds today. Only felt the breeze above 10,000'. No blowing snow. Wind did pick up after about 1330, but I was back down in the trees by then and couldn't see the affects.

Snowpack photos: 
Compression Tests failing on isolation. Facets under a hard wind slab.
3x5 ft. shallow wind slab kicked off in a steep gully.
Snowpit videos (tests, etc): 
Weather Observations
Blowing Snow: 
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