NTSB Probable Cause

THE PILOT-IN-COMMAND'S INTENTIONAL VFR FLIGHT INTO INSTRUMENT METEOROLOGICAL WEATHER CONDITIONS, AND HIS FAILURE TO MAINTAIN ADEQUATE ALTITUDE TO PROVIDE TERRAIN CLEARANCE. CONTRIBUTING FACTORS WERE: THE MOUNTAINOUS TERRAIN, ADVERSE WEATHER CONDITIONS, AND THE SECOND PILOT'S POSSIBLE REDUCED VISION DUE TO HIS VISION PROBLEM AND MEDICATION.