DURING PREFLT BRIEFINGS, THE PLT WAS BRIEFED TO EXPECT DETERIORATING WX CONDITIONS WITH ASSOCIATED FLT PRECAUTIONS FOR MOUNTAIN OBSCUREMENT, ICING & MODERATE TURBULENCE. THE WX BRIEFINGS WERE COMPLETE, EXCEPT DUE TO AN INOPERATIVE CIRCUIT, THE 0654 PRESCOTT & THE 0530 TO 0851 FLAGSTAFF OBSERVATIONS WERE NOT TRANSMITTED. WHILE ENROUTE, THE ACFT CRASHED INTO THE EASTERN FACE OF A MOUNTAIN, APPRX 9 MINORTHWEST OF THE SEDONA ARPT AT APRX 6000 FT MSL. THE ARPT MANAGER AT SEDONA ESTIMATED A 500 FT OVERCAST, VISIBILITY 5 MI WITH INTERMITTENT RAIN & SNOW SHOWERS. THE SEDONA ARPT WAS 1300 FT BELOW THE ACCIDENT SITE. ACCORDING TO AN NTSB WX STUDY, THE CLOUD BASES WERE AT 5000 TO 6000 FT MSL, CLOUD TOPS AT 11,000 FT, HIGHER CLOUD LAYERS ABOVE, FLT VISIBILITY 0 MI IN CLOUDS, MODERATE TURBULENCE BELOW 10,000 FT, SNOW & RAIN, FREEZING LEVEL 7000 FT.