Black Mtn, NW Trees - New Snow, Wind Loading, Mid-pack Weaknesses

Black Mtn, NW Trees
Submission Info
Wednesday, February 21, 2018 - 2:45pm
Red Flags: 
Recent loading by new snow, wind, or rain
Obvious avalanche path
Black Mtn, NW Trees 38° 2' 52.836" N, 119° 16' 28.164" W
Snowpit Observations
More detailed information about the snowpack: 

Observer: d lewis
Date: Feb 21, 2018, 9:50 PM
Loc: Black Mtn, NW Trees
Lat/Lon:38.0480, -119.2745
Elevation: 10350 f
Aspect: NW Angle: 28°
Signs of Instability: Hollow Sounding Snow, Wind Loading
Sky Cover: BKN
Precipitation: Snow, Very light snowfall < .5 cm/hour
Wind Speed: Light, subjective
Current Temp:-9°C
Blowing Snow: Previous W
Snow Depth: 120cm
Snow Temperature 20cm:-9.5° C 
Boot Penetration: 30cm

Comments: Toured up into the Frog Lake area below Black Mtn's NW face to assess new snow accumulation, bonding, & mid pack facets. 1-2" new consistently below treeline, 2-3" above, very light and prone to wind transport. Some previous cross loading of vertical terrain features from localized Westerly winds (skiers left to right). Found a suspended wind slab with audible characteristics at treeline, NW aspect, concavity. Hand shears varied greatly depending on overlying slab strength. Where loose, no result, where wind slabs present very easy to moderate (~10 cm thick). Stability tests - failed on weighting at new snow/ old snow interface but surface slab is very weak and not prone to propagation. Hard results @ 64cm on 2-m facets, Q3, NW aspect, 10350'. Light snow showers observed from June Lake north to VA Lakes. No avalanche or roller balls noted. If we get full amounts and wind forecasted with the approaching storm, anticipate numerous tender wind slabs. 

Snowpit or crown profile photo or graph: 
Snowpack photos: 
Snowpack Layering
Weather Observations
Blowing Snow: 
Cloud Cover: 
75% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Air temperature trend: 
Wind Direction: 
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: 

Light variable winds. Ocassional blowing snow from light gusty westerly winds. Cloud cover - strato cummulous from June Lake north to Virginia Lakes with light snow flurries. Very light winds aloft as evidenced by near stationary cloud cover. 

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