Wind effects and recent solar warming in the Sherwins,

SNOWPACK OBSERVATION
Mammoth rock, Lakes basin
Submission Info
Forecaster
Thursday, January 2, 2020 - 1:15pm
Red Flags: 
Recent avalanche activity
Recent loading by new snow, wind, or rain
Steve Mace 37° 37' 2.694" N, 118° 59' 34.674" W
Snowpit Observations
More detailed information about the snowpack: 

It was a pleasant day in the Mammoth area today. I left the car mid-morning at the mammoth rock trailhead with two goals. First, I was hoping to gauge the impact from yesterday’s strong northwest winds on mid-elevations, and second to get a feel for surface warming on solar aspects.  Ascending above Mammoth rock, it became immediately apparent that the winds yesterday had effected surface conditions even in more sheltered treed areas. Signs of recent wind transport including uneven snow surface, mild cracking, recently filled skin tracks, and thin wind skins were observed throughout the terrain.  On the ridge, I observed some recent cornice growth and recent deposits as thick as 30 cm. I did not observe any recent avalanche activity, and I was not able to trigger any with targeted ski cuts. The recent deposited dense wind board was pencil hard and fully supportable. However, stability tests conducted in a quick snowpit right off the ridge showed the potential is still there.  Multiple hand sheers and compression tests failed with isolation.

Further down the slope where the wind board became thinner, only 5 cm or so, and I began to break through on my skis.  I was able to get a few dinner table-sized blocks to break loose here though the risk of a larger avalanche was minimal.  Descending the north-facing trees back to old Mammoth road, I was able to find nice turns by sniffing out alleys in-between recent, refrozen tracks.  The wind textured soft snow proved to be quite enjoyable.

After hitting Old Mammoth road, I skinned out to the Lakes basin to get a look at some more solar aspects.  Upon reaching the Pack station, I saw a sizable loose wet slide on the backside of Sherwin ridge. Skinning up to get a closer look, it became apparent that this slide most likely happened yesterday. Despite the relatively warm air temperatures today, the high-level cirrus clouds seemed to filter enough solar radiation to keep the surface snow from warming too much today. Surface conditions at 1 pm were still cold, and a 2 cm melt freeze crust was present.  This particular slide looked to have started as a point release near a tree and run about 500’ entraining quite a bit of snow.  The debris pile was almost 5‘ deep, and it ran on the ground.

Snowpack photos: 
Weather Observations
Blowing Snow: 
No
Cloud Cover: 
25% of the sky covered by clouds
Air temperature: 
Above Freezing
Wind Speed: 
Moderate
Precipitation: 
None
Air temperature trend: 
Static
Wind Direction: 
North
Accumulation rate: 
None
More detailed information about the weather: 

Moderate winds, and warm temperatures made for a pleasant day in the mountains today. temperatures remained above freezing all day though partly cloudy skies and moderate winds kept things feeling brisk. 

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