Unstable Results on Surface Hoar on Rubicon Peak

Supportable frozen rain crusts existed on the snow surface up to 7400 ft on Rubicon Peak today. Between 7400 and 8200 ft. this crust became variable and sometimes would support the weight of a skier and sometimes would break under the weight of a skier. Above 8200 ft. a layer of heavy snow existed on the surface that would also sometimes break under the weigh of a skier. Below this heavy snow and the rain crusts the upper portion of the snowpack showed some signs of settlement and consolidation, but a buried surface hoar layer still existed about 70 cm down in the snowpack. Tests on this surface hoar layer still produced unstable results. These tests showed that if this layer breaks the resulting fracture could still travel through this buried surface hoar layer and could still result in a large avalanche. 

On wind loaded near and above treeline slopes hard wind slabs existed and Extended Column Tests on these wind slabs also showed that fractures could still possibly propagate below these wind slabs. 

Photos 1 and 2: 6mm surface hoar buried on Jan. 9th. This layer is currently about 70 cm below the surface.

Video: PST 25/100 END on the buried surface hoar layer. 2 ECTPs also occurred on this layer. See pit profile for other details.