Wind Slab Avalanche near Stanford Rock

Our plan was to go on an early morning tour before the storm rolled in.  I read the morning forecast and saw gale force wind event with wind slabs being the primary concern.  We decided to go to a below treeline zone that we have known to be well sheltered from the wind.  This is a zone we have ridden many times including multiple times in the past week where we experienced excellent glade riding conditions with stable snow.  The large old growth trees and familiarity with the zone lead us to be complacent, seeing as we decided on tour to ride a small chute area we had seen earlier in the week.  While this area was well below treeline, clearly the winds were strong enough to transport a significant amount of snow and build a wind slab in the zone of interest.  In hindsight, texture on the snow surface and the slightly convex terrain should have been clear warning signs, as were the signs of blowing snow even in the densely treed area.  The forecast did say wind slabs were possible in isolated below treeline areas, which this was a prime example of.  The slope released as I made a turn through it, and it carried me down into the trees below.  I was luckily able to stay on top of the snow with my board below me and avoid any large trees. The slow moving nature of the avalanche suggested that impact with a large tree would have been relatively low consequence (going head first into a tree at that speed would have been unfortunate but not serious).  Eventually I was able to stand up on my board as the slide slowed and ride out of the debris field.  My partner immediately rode down after me when he saw the slide, and released another small section of slope as he went.  I was able to radio to him that I was okay as he was preparing to get his probe from his pack.  I'm grateful he was quick to act and ready for the worst case.  A slide like this in terrain with a steeper angle, a longer run, sharp rocks, and/or large cliffs would have carried with it a significant chance of injury or worse.  

Upon reflection, I feel that the main cause of today's incident was human factors.  Firstly, we assumed that a below treeline zone where we had significant experience riding in without ever seeing any signs of instability would be safe.  Second, our complacency built up from the past few weeks of excellent, stable powder riding in the past few weeks meant that we were did not acknowledge the obvious warning signs (strong winds and blowing snow even in the trees).  This incident was entirely avoidable, given that the surrounding terrain offered plenty of excellent turns in shallower angle, non-convex terrain.  Another factor contributing to our decision making was the desire to ride a line we had seen from below a few days ago.  This is a good reminder that conditions can change quickly and at any time, so when returning to a zone it is best to evaluate the conditions from scratch, rather than relying on previous experience no matter how recently.

In summary, the incident was physically harmless to the rider involved, but an excellent reminder that managing human factors is an essential part of safe recreation in or near avalanche terrain.  Review the red flags, acknowledge when you observe them and take a moment or two before you drop to check in with whether there are any reasons (obvious or not) that you shouldn't be entering certain terrain.