Persistent Weak Layer on Rubicon Peak

Our group skied up Rubicon Peak and dug a few snow pits as a training for a local search and rescue team. After completing our first lap up, we dropped down to approx. 8900' and dug three pits on an North-East facing aspect and a 30 degree slope angle. The snowpack appeared to be well consolidated and had only one degree of temperature gradient increase (-5 to -4 degrees C) from the bottom of the pack through the top. We performed an Extended Column Test, Isolated Column Test, Shovel Shear Test, and a Rouche Block Test. None of the tests produced any significant findings (no tests reacted under normal parameters). However, we did find the persistant weak layer described in today's forcast and that we suspect caused the large avalanche on Castle Peak yesterday. This layer was located approx. 120cm deep in the snowpack. When we did get it to release (extra hard hits outside of normal testing parameters), it produced a quality 2 shear composed of granular crystals and an entirely cohesive slab all the way through the top layer of the snowpack. We decided that the weak layer was very deep and that the slope was safe to ski since it was highly unlikely that we would be able to affect the weak layer. After completing our first lap, we climbed back up and completed an additional lap down the North aspect before traversing back to the lower ridge and parking area. I apologize for not getting more accurate pictures.