Wind Slabs on the Sherwins

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SNOWPACK OBSERVATION
Submission Info
Forecaster
Thursday, February 22, 2018 - 11:15am
Red Flags: 
Whumphing noises, shooting cracks, or collapsing
Recent loading by new snow, wind, or rain
37° 36' 31.536" N, 118° 59' 32.0388" W
Snowpit Observations
More detailed information about the snowpack: 

Toured to the top of the Sherwins in near whiteout conditions looking for wind slab formation and sensitivity. Everything pointed towards touchy wind slab developement this moring on NW-N-NE facing slopes, the slabs just weren't very big by the time I was down around 1230pm. Hand shears failed consistently either on isolation or with easy force under 4F hard wind deposits in F hard fragmented storm snow. Shooting cracks up to 2m long were common in fresh wind deposits (see ski tips photo). Ski cuts had many small results ranging from just localized plating to small slabs breaking out from the surrounding snow (see video of tracing the outline of a small slab). Cross-loaded openings along the lee side of sub-ridges were generally more sensitive than just below the Sherwin ridge. Wind slabs ranged from 1" deep to 8" deep the higher I got. Blowing snow was strong, primarily in turbulent suspension, and slab deposition varied greatly with subtleties of terrian. No visible natural avalanches.

The general snow structure below the ridge was of F-4F hard wind broken grains or wind packed rounds on top of F hard fragmented storm snow on top of 1F-K hard either previous wind or previous melt-freeze crusts that were decomposing into facets in many places on top of large F hard facets. In some places well developed facets were either at the surface (more sheltered areas) or directly below storm snow (see crystal card photo). In most places with shooting cracks or small slab failure, the weak layer was not yet these facets but F hard storm snow under the wind packed slabs.

Winds were strong with very strong gusts, generally from the SW to W, but local eddying was building drift on many aspects (see blowing snow video for an idea of general conditions). Snowfall ranged from light to moderate (S1 to S2). Temperatures were cold and windchill was fridgid.

Obstacles are still a huge concern. I did very little skiing and a lot of side slipping and booting down on my rock skis.

Snowpack photos: 
Shooting cracks in wind slabs
Large near surface facets in some areas
Snowpit videos (tests, etc): 
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Strong
Precipitation: 
Snow
Air temperature trend: 
Static
Wind Direction: 
Southwest
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: 

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