Forecaster Observation - Sub-Shields, southern Glacier Park

We chose Sub-Shields for our tour due to the high winds that were recently recorded in John F. Stevens Canyon. We were in search of wind slabs to note their distribution and strength.

On our ascent we found substantial evidence of wind transported snow at mid-elevations on the southeast ridge of Sub-Shields.  There were numerous fresh wind features in the trees and fresh cornices on easterly aspects. We kicked, with our skis, a sampling of these cornices and were able to get easy failure in each instance. The cornice only broke as wide as our skis and did not propagate.  However, the ease of failure and the mass of cornice that would break was impressive. Obviously, a lot of snow had been recently transported. 

We dug a pit on a wind loaded northeast aspect at 6920 feet.  Snow depth was 245 cm with the top 27 cm composed of relatively cohesionless new and wind blown snow.  Below this was a 1 cm layer of decomposing surface hoar. At 94 cm below the surface there was a 2 cm thick pencil hard rain crust. Below the crust was strong (1F+) snow.  

Stability tests resulted in no propagation but we did have easy failure in the surface hoar layer in both compression and extended column tests (CT10 and ECTN10).

With the abnormally strong recent winds we theorized that the wind deposited the new snow at a lower elevation than what is "normal". We then descended the east facing bowl assessing the snow surface for evidence of wind slab/cohesive qualities. No wind slab was found on our descent.