Observed on the way to ski a north facing above treeline slope, 11.5-12k (i believe on the ridge to lookers right of no name). We dug a rudimentary pit about 4 feet deep at a 35-40ish degree angle and found 2-3 inches of soft snow bonded to a harder layer that went down at least a few feet. A quick extended column test showed that these layers had bonded well together as i couldnt get the column to slide with heavy shoulder strength impacts. My gut reaction is the major difference between the aspect i skied and the aspect with an observed avalanche was wind loading, although sun may have been a factor.