Isolated Wind Slabs, South Peak

 
 
 
 
 
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SNOWPACK OBSERVATION
Submission Info
Forecaster
Tuesday, February 13, 2018 - 5:00pm
Red Flags: 
38° 2' 30.48" N, 119° 15' 15.48" W
Snowpit Observations
More detailed information about the snowpack: 

Toured up the saddle between Mt. Olsen and South Peak and traversed W across the E-NE-N aspects of South Peak at about 10,800' looking for reactive wind slabs and current wind loading.

On the way up it was clear that W aspects were stripped and that E aspect had been crossloaded. However, that seems to have happened either early in the storm yesterday or during the pre-frontal winds on the 10th and the 11th because about 15cm of low density new snow from yesterday's showers was largely un-affected by wind except for a little evidence of wind transport above 10,600'. Winds today across E-N aspects were calm to light and generally from the E-SE. But on favorable features, like at the top of the saddle, moderate S winds were occasionally transporting snow onto northerly aspects (the wind over the saddle and E ridge of South Peak were continuous, but there's still not a whole lot of snow on most S aspects available for transport). Hand shears on the way up pulled easily through the unconsolidated new snow, or with hard force in facets under the most recent wind crust. The general snow structure consisted of new low density snow (F-) on top of very hard previous wind slabs (P+) on top of a thin layer of facets (F) on top of a melt-freeze crust with more soft facets under that. Just at the saddle and along the E ridge to the summit of South Peak there were indeed some denser (F+/4F-) new wind slabs approximately 20cm deep. I stomped on them and got a few chunks to break off and some local cracking, but there was definately stored energy in there and I'd attribute the limited nature of the cracking to the size and discontinuity of the slabs rather than to them being unreactive. They were reative, just small and isolated. In most places, the new and un-affected snow sat atop previously deposite wind slabs that were very hard (P+) and bout 10-20cm thick. I did get some very small results from a ski cut on a steep (40 degree) NE slope at 10,600' where the older wind slabs were thin enough for me to break through to the facets underneath (see attached photos). Other than that, pretty quite day out there. Most storm snow was supprisingly un-affected by wind (even looking up slope to almost the top of South Peak where most N facing slopes had been stripped down to almost rock). A few small natrual sloughs had released in the storm snow. I would expect that southerly aspects with enough snow on them before yesterday's storm (say, Virginia Pass near Frog Lake) would indeed have some wind slabs near the top that a skier could trigger today.

Snowpack photos: 
Very small results from a ski cut
Thin wind slabs on top of facets
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
50% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Light
Precipitation: 
None
Air temperature trend: 
Warming
Wind Direction: 
South
Accumulation rate: 
None
More detailed information about the weather: 

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