What happened
During an en route climb to cruise altitude, the pilot of a PA-32R-300 elected to turn into a box canyon. At the moment the turn was initiated, the pilot believed the aircraft's rate of climb was sufficient to clear the ridge located at the end of the canyon.
Upon entering the canyon, the aircraft encountered an area of downdrafts. This descending air decreased the aircraft's rate of climb to a level that prevented the pilot from outclimbing the rising terrain ahead. Due to the narrowness of the canyon, the pilot determined that a successful reversal of course was not possible. Consequently, the pilot continued up the canyon, which resulted in a controlled impact with the terrain.