Wind Slabs, Virginia Lakes

SNOWPACK OBSERVATION
Submission Info
Forecaster
Tuesday, February 27, 2018 - 1:30pm
Red Flags: 
Whumphing noises, shooting cracks, or collapsing
Recent loading by new snow, wind, or rain
38° 2' 22.92" N, 119° 15' 6.48" W
Snowpit Observations
More detailed information about the snowpack: 

Toured up the saddle between Mt. Olsen and South Peak in Virginia Lakes looking for recently deposited wind slabs on N aspects and new wind slabs from this morning's N winds on S aspects.

N Aspects: Wind slabs deposited on Sunday night/Monday were still reactive though less touchy than indicated in observations yesterday. Most slabs were found on NE aspects. Several kick tests in small wind drifts failed ~25-30cm down in F hard facets under 4F hard wind slabs. Several CTE and CTM SP reults down 27cm in F hard facets under 1F to 4F hard wind slabs. 2 ECTP results in the same layer at 2 different locations (see ECT video as an example). The snowpack structure in sheltered areas in the trees closely resembled that in the test sites on NE aspects. The snowpack on NW aspects was much thinner (60cm), mostly faceted, without wind drifts, and had inconclusive test results (however, the facets are well developed and may become a problem after a lot of new snow on Thursday/Friday). We encountered plenty of other hollow unsupported slabs that cracked under our weight on the way up.

S Aspects: North winds this morning had stripped the top of the saddle and built fresh wind slabs and cornices on the S side of the pass. Stomping on the cornices on the S side produced many D1 results (see cornice stomping video as an example). The slope angle in the start zone of these failures was 35 degrees, most slabs were ~30cm thick and 10'x10' and ran between 40 and 60'. The slabs were 4F hard wind deposite rounds, the weak layer was F hard wind broken fragments, and the bed surface was K hard previous wind deposit. *I would not usually had used this slope as an inconsequential test slope, but given the poor snow coverage 60' was about the max that snow could slide. Test slopes should have little to no consequence so that if they slide you wont get hurt!*

By 11am when were started up the saddle winds were calm and cloud cover was scattered.  Winds were calm all afternoon, but had obviously been blowing and moving snow (N winds) all morning. No natural avalanches observed today anywhere.

Snowpit videos (tests, etc): 
Weather Observations
Blowing Snow: 
No
Cloud Cover: 
50% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Calm
Precipitation: 
None
Air temperature trend: 
Warming
Wind Direction: 
Accumulation rate: 
None
More detailed information about the weather: 

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