NTSB Probable Cause

CONTINUED VFR FLIGHT BY THE PILOT INTO INSTRUMENT METEORLOGICAL CONDITIONS WHICH RESULTED IN AN IN-FLIGHT COLLSION WITH TERRAIN. RELATED FACTORS WERE: FAILURE OF THE PILOT TO USE A PREFLIGHT BRIEFING SERVICE, HIS DECISION TO INITIATE FLIGHT INTO KNOWN ADVERSE WEATHER, THE ADVERSE WEATHER CONDITIONS, THE PILOT'S VISUAL PERCEPTION AT DUSK, AND THE RISING/MOUNTAINOUS TERRAIN.