Negatives - Wind Slabs

SNOWPACK OBSERVATION
Negatives - Wind Slabs
Submission Info
Forecaster
Wednesday, February 14, 2018 - 2:45pm
Red Flags: 
Recent avalanche activity
Whumphing noises, shooting cracks, or collapsing
Recent loading by new snow, wind, or rain
Obvious avalanche path
Negatives - Wind Slabs 37° 43' 37.1856" N, 119° 5' 43.26" W
Snowpit Observations
More detailed information about the snowpack: 

Tour­ed toward the Negatives today to assess Wind Slab instabilities. On the drive from Mammoth noted extensive snow banners over the mountains from June Mountain north to Lee Vining from southwesterly to westerly winds. As I pulled into the parking lot of June, banners extended from the summit of San Joaquin Mountain and Carson Peak from southwesterly flow aloft. At ~ 7500’ winds were light but clearly blowing moderate to strong in the alpine from mid-morning through mid-afternoon when winds seemed to be ease a bit, becoming less gusty but still transporting snow. Generally, 4” to 8” of new low-density snow coverage from the past couple of days, which is very transportable, as evidenced today. Overnight, surface hoar formed throughout the lower and mid-elevations into the alpine. Size appeared to range from 5 to 10 mm and still present in protected areas. At treeline the surface hoar was being broken-up by surface winds with 2 mm to 5 mm particles filling the skin track on ascent. Winds were very gusty and the direction variable below the ridgelines with extensive crossloading from what appeared to be northwesterly eddies. Cracking noted on ascent on an isolated loaded feature. The snow where unwind-effected lacked slab-like characteristics, very loose and light, shear test negative. Where Wind Slabs present, failed on isolation or easy but test slopes produced no results. The new snow is bonding to the older icy surface while the Wind Slabs are still developing a bond to the underlying new low-density snow. Noted three debris fields from recent avalanches (2, D1), one possible D2, difficult to fully ascertain since the debris was partially covered. In sheltered areas, the mid-February sun is strong enough to heat up the top 2 cm despite the cool daily temperature, barely moist but noticeable clumping. Some riming noted on the trees from treeline into the alpine. Creeks are opening up in the meadow below the Negatives with open water.    

Snowpit or crown profile photo or graph: 
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
50% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Strong
Precipitation: 
None
Air temperature trend: 
Cooling
Wind Direction: 
Southwest
Accumulation rate: 
More detailed information about the weather: 

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