Surface hoar @ Rubicon, 40cm ECTP15 SC

Location Name: 
Rubicon Peak N Face
Region: 
West Shore Area
Date and time of observation: 
Sat, 12/19/2015 - 10:40
Location Map: 
United States
38° 59' 29.5116" N, 120° 8' 1.0716" W
See map: Google Maps
US


Red Flags: 
Recent loading by new snow, wind, or rain
Observation made by: Public
Snowpit Observations
More detailed information about the snowpack: 

Looked for surface hoar layer and it was not obvious during layer ID with a gloved hand and crystal card, however I was able to propagate a failure on surface hoar layer via ECT.

ECTP15 SC @ ~40Cm below surface. Sudden collapse was obvious by sound and feeling during ECT test. There was a very minimal vertical collapse and it was not really observable visually. Pulling out the slab showed a resistant quality to the shear and revealed flattened feather-form hoar grains roughly 5-10mm in size. My best guess would be that the hoar grains had been previously compressed by the weight of new snow and flattened out completely during ECT test.

No whoomphing or collapsing was observed while skinning or skiing. We avoided steeper rollovers and kept with well-anchored terrain.

A soft windslab was beginning to form on ridgeline areas that would break off of the skintrack, but winds died down throughout the day and the soft slab became less apparent and seeminly less reactive.

Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
75% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Light
Precipitation: 
Snow
Air temperature trend: 
Cooling
Wind Direction: 
Southwest
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: 

Wind direction over ridgelines was southwest, but wraparound was creating light upslope NE gusts that increased local snow accumulation rates. Sky condition was broken, with new snowfall rates at less than 1 CM per hour.