Variable wind slab at The Sisters

The convoluted terrain between Black Butte and The Sisters provided a good opportunity today to look at multiple aspects in relation to recent shifting winds. I found no signs of instability on NE/E aspects, and conflicting signs of instability on more recently loaded W/NW aspects.

The day began with a cool and cloudy morning. As soon as clouds cleared around 11am, temperatures climbed noticeably and the ~3 inches of fresh snow became sticky on sunny aspects. Winds were moderate out of the SW but no current wind transport was observed. I did not observe wet instabilities by my mid-afternoon departure.

On NE/E aspects, I was able to find a graupel layer at a similar height to a reactive graupel layer observed at Indian Valley a few days ago. Numerous snowpack tests did not indicate this layer was a concern today.

W/NW facing test slopes with soft wind blown snow produced shooting cracks close to 1 foot deep, but slab thickness quickly tapered to a few inches. I could still see large stellars and plated stellars in the weak layer. No faceted grain types were observed. On similar aspects near ridgeline, the surface snow was quite firm and supportable. I heard/felt several "whumpfs" that propagated far enough to be spooky, but I dug in several places and believe the weak precip layer was generally shallow. When I moved to the edge of where I perceived the whumpf to propagate, I tried ECTs, which did not propagate.

Pic 1: A shooting crack on a W facing test slope.

Pic 2: Graupel about 1 foot down on NE/E aspects. ECTs did not propagate and CTs were non-planar.

Pic 3: After experiencing whumpfs on firm W/NW aspects, the only discernable weak layer I could find was not very deep.

Pic 4: The most appealing descent line was very similar to terrain where I had been experiencing whumpfs, so today was a good day to enjoy the views and skip the most obvious line, just left of center. Note how wind effected everything else is.