Sunday 4/29, from South Lake, booted up Bishop Pass/Treasure Lakes summer trail to below Treasure Lakes, then skinned up to 10,900' (point marked on map). Turned around a little before 11AM because of building cloud cover obscuring sun and causing snow surface to refreeze. We traveled on NW, N, and NE aspects. When booting, the occaisional post-hole revealed the bottom half of the pack to be a cohesionless mush of wet depth hoar (total depths in 60-100 cm range). Probing with boots and ski poles indicated the weak snow is present at the bottom of the pack basically everywhere we we went. The upper half to the pack was generally strong enough to provide good booting and skiing. A few glide cracks are developing where the snow is on rock slabs, and on the low angle meadow at 11,500' there are cracks in the snow surface where the upper part of the pack has collapsed into the basal mush. In a few days, when the temperatures come back up and spring sun returns, the weakness at the base of the pack may present an afternoon wet slab problem.