Naturals in Sherwins

AVALANCHE OBSERVATION
Sherwins

Drainage:

Submission Info
Member
Saturday, April 8, 2017 - 12:30pm
Red Flags: 
Recent avalanche activity
Recent loading by new snow, wind, or rain
Trigger type: 
Natural
Aspect: 
Northeast
Weak Layer: 
Storm Snow
Terrain: 
Near Treeline
Elevation: 
10 000ft.
Number of similar avalanches: 
2
More detailed information about the avalanche: 

Observed debris at the bottom of Dempsey Don't almost to the bottom of the path (stopped a few 100 feet before the meadows). We also saw evidence of a natural slide in The Hose at about half way down that had taken out some smaller trees. In both cases the slide debris was covered by at least 10-20 cm of new snow, so they likely occured late afternoon/evening yesterday (Friday). Visibility was generally poor and still storming at the ridgeline, so we weren't able to see any crown lines or get a sense of what exactly released.

We started at the Old Mammoth Road trailhead and toured up by Mammoth Rock. We dug a pit at 9500' on a somewhat sheltered 30 degree NNE slope. There was 100 cm of new snow with 20 cm of fist hard light snow from overnight on top, then another layer of 4F snow extending down to 40 cm below the surface. Below that, the new snow increased in density fairly uniformly from 1F to P- at about 100 cm. The old snow was still wet, but I didn't observe any free water in the back.

Test Results:

CT11 Q3 15cm

CT15 Q2 35cm

ECTN 11 15cm

ECTP 21 35cm

Ski Pen: 13cm

Boot Pen: ~95cm

The interface between the new snow and the old snow a meter down appeared fairly well bonded today - at this point I'd say the primary avalanche concern is new wind slabs forming near ridgelines. The density change 40cm down also has propagation potential although it would likely be fairly hard to trigger from a skier.

We skied trees between The Hose and Dempsey's, and another lap to skier's left of The Hose, but we did not observe any signs of instability other than the slide debris.

Blowing Snow: 
Yes
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Strong
Precipitation: 
Snow
Air temperature trend: 
Cooling
Wind Direction: 
Southwest
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: 

Gusty winds near the ridgelines.

Sherwins 37° 36' 41.8104" N, 118° 59' 30.4944" W

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