Lee Vining - Snow Conditions - small loose dry avalanches - spindrift

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SNOWPACK OBSERVATION
Liberty chute apron
Submission Info
Forecaster
Wednesday, March 13, 2019 - 9:30pm
Red Flags: 
Recent avalanche activity
37° 55' 20.7156" N, 119° 12' 39.9996" W
Snowpit Observations
More detailed information about the snowpack: 

Toured up V bowl and into the basin below the dana plateau in the area of the Third Pillar couloir and Liberty chute. East aspects had a fairly robust 1-2"crust while Northerly aspects for the most part harbored soft snow where sheltered. There was wind transport up high, but was not actively moving snow all day... it was more sporadic with isolated gusts for the most part. There were some active small loose dry avalanches pouring down from the chutes througout the day, but there was not anything significant of size or run. As we neared the top of our skin track, before booting up Liberty chute, I skinned over an obviously loaded area of the apron. There was recent small loose dry depostion on top of this wind loaded feature. When I stepped over the debris, a small 30' panel of hard wind slab snow collapsed and shifted a few feet down slope (see attached photo). The extra weight triggered this 15cm thick (1F) hardslab that was underneath the top 20cm of powder and sitting on top of (4F) snow. It made me wonder if a cornice fall with an extraordinary amount of weight could trigger a larger windslab where windlslabs were present. Much of the snowpack in the alpine had been swept over by previous loose avalanches and was much more firm and consolidated. There was 20-25cm of (F) powder on average on a variety of subsurface layers depending on minor changes of aspect and angle in the aprons of the chutes.  A bergschrund was beginning to open at 10700' on Liberty chute (see photo).

I dug a 100cm deep snowpit next to where I got the small windslab to collapse in the apron of liberty chute.

10,683ft elevation   N 12deg aspect   39slope

CT21 SC Q3 @ 35cm below surface (at interface between 1F windslab and 4F snow beneath)

ECTP23 RR Q3 @ 35cm below surface

There was much spatial variability and these tests were not representative of the whole area, but showed there were possible areas of instability to be on the lookout for, namely smooth windloaded features which had not had previous avalanches run over the terrain. Stability tests showed Hard scores and the interaface between the windslab and softer snow below was resistent planer in nature and did not shear cleanly. Hand shears during the day where all moderate in pull and nothing was Sudden Planar.

Snowpack photos: 
Snowpit videos (tests, etc): 
Weather Observations
More detailed information about the weather: 

Completly clear day, with nice chilly temps.

Stayed at 14F for most of the day in the shade above 10000'

Light winds while travelling in the cirque below the dana plateau, but there was northerly and westerly winds transporting snow off the plateau.

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