The flight crew's failure to maintain airspeed while maneuvering to exit an area of rising terrain, which resulted in an exceedance of the airplane's critical angle of attack and an aerodynamic stall. Contributing to the accident was the flight crew's decision to continue the takeoff toward rising terrain that likely exceeded the airplane's climb capability, the lack of adequate weather reporting available for wind determination, and the lack of documented training for an airport requiring a non-standard departure.