Skier Triggered Wind Slab Avalanche on Rubicon Peak

Driving down the West Shore we had to slow to a crawl several times due to blowing snow. These strong winds and blowing snow at Lake level clued us in to the fact that wind slabs and wind affected snow could extend into the more sheltered areas on Rubicon. We noted 8 to 10 inches of new snow in the parking lot at 10:40 in the morning. Skinning up we could see blowing snow at all elevations and could feel a more cohesive layer on top of a less dense layer both with our pole probes and when we stepped off the skin track to break trail. We dug several hand pits and sought out small inconsequential test slopes to see how these layers were bonding. When we tested undercut test slopes, our ski kicks could trigger large shooting cracks in below treeline terrain.

At one point where we stopped to dig a pit, we were sharing information with another backcountry skier who was on his second lap. He told us that a party had triggered a small wind slab avalanche on the leeward side of the summit of Rubicon. No one was injured or buried. We continued up to the ridge and continued focus on small test slopes to gather more information. Near treeline, we started to trigger shooting cracks on small wind-loaded test slopes.  When we got to the site of the skier-triggered wind slab just below the summit of Rubicon on the NE side, we could still see the crown line but it had almost filled back in. The avalanche was about 70 to 100 ft. wide and looked like it had been about 8-10 inches deep and run downhill for about 30 ft. 

We chose to ski lower angle terrain and avoid the wind-loaded terrain. Coverage was pretty good above 7500 ft, but there were still some obstacles above that elevation. Below 7500 ft we skied slow and cautious due to the plethora of rocks, stumps, and logs still either close to the surface or sticking out of the snow.

Photo 1: Mostly filled in crown line from a small skier triggered wind slab avalanche about 2 hours before we got there. NE aspect, 39-degree slope, 9100 ft. The crown goes from where I am taking the photo to where my partner is standing.

Photo 2: Skier triggered shooting cracks resulting from a storm slab instability on an undercut slope.

Photo 3: Skier triggered shooting cracks on a wind-loaded test slope.

Photo 4: Lots of obstacles below 7500 ft.