We were surprised by multiple signs of instability during a tour on North facing terrain just West of Mill 3. We did not dig a pit, but our layer of greatest concern was the atmospheric river interface, buried approximately 15cm down at 6,000 feet, and 30 cm down at 8,000 feet. We got one prominent collapse climbing dense wind slab in a steep North facing gully at about 6,300 feet, and throughout the tour, we observed quite a bit of isolated cracking in surface wind slabs. Quite a bit more cracking than we would expect given that the interface has had a full week to stabilize.
We had several theories about the weak layer (poorly bonded ice crust, thin facet layer on the ice crust, recent slab development when wind picked up late in the week), but we weren't confident enough to categorize the exact nature of the weak layer, especially since we were observing surprisingly touchy snow above and below the atmospheric river event rain line. Given our deep uncertainty, we completely altered our route to stay out of avalanche terrain.