Positive Ski Cutting Results, Hammil Bowl

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SNOWPACK OBSERVATION
Submission Info
Forecaster
Tuesday, February 20, 2018 - 1:45pm
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Recent loading by new snow, wind, or rain
37° 34' 17.4" N, 119° 0' 11.52" W
Snowpit Observations
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Toured up to the top of Hammil Bowl from the Tamarack ski trails in the Lakes Basin looking for wind slabs at upper elevations and general conditions near and below treeline. Cold day, with Tair = -5 and Tsurf = -12 down at 9100' at 11am. Calm winds except above ~9800' by 12pm when the started to pick up to Light from the S. Winds increased to Moderate with snow transport in saltation and turbulent suspension at the very top of the Crest (see video). We put in 2 ski cuts across small drifts on the sidewalls at the top of Hammil. First ski cut, skier's R side - NNW facing, had no results. Second ski cut, skier's L side - NE facing, kicked of a small D1 wind slab. The slab was up to 15cm deep, averaging 10cm. The slab was 4F hard wind deposited rounds and the weak layer was F hard wind broken snow from yesterday or Sunday. The bed surface was P+ hard old wind board. Slide was 10'x10' and ran 50'. Slope in the start zone was 40 degrees (see attached photos). *Ski cutting is an advanced skill requiring training and experience.*

Boot pen = 30cm through 4F hard recent wind slabs just below the top of the Crest, but there was no cracking and these slabs were not a single deposit but layers of 2-5cm thick soft wind crusts with softer wind fragmented storm snow between. Slabs stretched about 10 to 20' down the slope.

Previous winds had been from the NE locally, and W facing test slopes at 10,000' in previously deposited drifts had little result, some minor cracking, sloughing. Many small D 0.5 sloughs on very steep N and NE facing slopes from yesterday or Sunday. Most storm snow was unconsolidated F hard and between 10 and 15cm deep sitting on P hard old wind crust, or F hard facets.

Did 2 sets of snowpack tests. First one was near treeline at 9800' on a NNE aspect, 9 degree slope where snow depth was 113cm. CTE PC down 12cm at the interface of 4F hard decomposing and fragmented storm snow (DFs) on top of F hard decomposing and fragmented storm snow (storm snow was just starting to settle). CTM SC down 17cm at the interface between 4F hard DFs on top of F hard facets (FCs). CTM SC down 53cm in F+ hard FCs under a 1F hard melt-freeze crust. ECTs to test those interfaces did not propagate. Second set of tests was above treeline at 10,400' on a NE aspect, 31 degree slope where the snow depth average was 110cm (talus below). CTM PC down 13cm at the interface of 4F- hard wind fragmented storm snow on top of F- hard FCs. No other repeatable results at this site.

The very hard old wind board under the recent storm snow got us sliding downhill near the top. Boot crampons fixed that problem.

General impression: While previous winds were light enough to leave the recent storm snow largely un-effected (maybe small, isolated, and stubborn old wind slabs) isolated, small, but touchy wind slabs began forming around noon today in the Mammoth area.

Snowpack photos: 
D1 wind slab results from ski cutting
Slab depth 10cm
Snowpit videos (tests, etc): 
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