Stubborn Wind Slabs, Warming: Sherwins

SNOWPACK OBSERVATION
Submission Info
Forecaster
Tuesday, April 17, 2018 - 3:00pm
Red Flags: 
Recent avalanche activity
Recent loading by new snow, wind, or rain
Rapid warming
37° 36' 35.9568" N, 118° 59' 34.9044" W
Snowpit Observations
More detailed information about the snowpack: 

Knowing full well what I was getting into I waited until the mid afternoon to tour up the Sherwins to see how high up the warming would be changing the recent storm snow and to see if any wind slabs remained sensitive. That being said: mandatory skin wax conditions, sticky. Elevations observed: 8323'-10,000'. Times observed: between 130pm and 330pm.

Snow was transitioning and moisteing in the top 5-10cm up to 9500' above which the snow remained cold winter snow. The storm snow from Monday is still not well bonded to the underlying melt-freeze layer and tended to sluff or at least slide on steeper slopes while skinning. Surfaces ranged from soft DFs in truely sheltered and shady areas on N facing slopes, to moistening transitional snow with very small rollerballs with any sun exposure at all, to 5-15cm thick F+ to 4F hard wind skins. Many hand shears failed with easy force or on isolation under the wind skins or under the settling transitional moist snow. All hand shears failed within the F- hard, dry storm snow above the melt-freeze layer. Kick tests, cornice drops, and ski cuts across the top of the Poop Chute, the Hose, and a skier's L side chute entrance to Mammoth Rock Bowl all had minimal results: some cracking (up to 1m), some small chunks breaking off, some sluffing. Storm snow was settling down with the thawing to about 20cm deep on top of the melt-freeze layer. By 3pm transitional moist snow that was now in the shade was re-freezing with a zipper crust on top.

At the top of the Sherwin ridge sushine was intense but temps were still below freezing: -1deg C. No slides were visible on the Mammoth Crest. Some small D0.5 to D1 skier triggered slides from yesterday on the top of the Hose.

Snowpack photos: 
Minor sluffing, cracking, and plating from test slopes and cornice drops
Hand shears failed on isolation under 5cm thick wind skins and moistening snow over dry winter snow
Mammoth Crest under intense spring sun
Mammoth Crest under intense spring sun
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
Clear
Air temperature: 
Below Freezing
Wind Speed: 
Light
Precipitation: 
None
Air temperature trend: 
Warming
Wind Direction: 
North
Accumulation rate: 
None
More detailed information about the weather: 

Light N winds at ridge tops with some very minor and occasional stripping of soft storm snow from the top of Mammoth Rock Bowl and the Hose (creep). Clear skies, intense solar radiation.

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