THE ACFT COLLIDED WITH THE GROUND IN A NEAR VERTICAL DIVE. PRIOR TO THE ACCIDENT, WITNESSES HEARD THE ENG AT HI POWER UNTIL MOMENTS BEFORE IMPACT. THEY REPORTED THE WX WAS CLOUDY & COOL WITH LIGHT RAIN BEGINNING TO FALL, MIXED WITH SNOW. THEY REPORTED THE CLOUD BASES WERE VARIABLE WITH AREAS OF LOW CEILINGS & VISIBILITIES. ABOUT 11 MI NORTHWEST AT WILLOW, AK, THE 1050 AST WX WAS IN PART: 12,000 FT BROKEN, VISIBILITY 50 MI, WIND 310 DEG AT 6 KTS, TEMP 38 DEG. THE FREEZING LEVEL WAS FORCASTED TO BE AT 12,000 FT. LIGHT TO OCCASIONAL MODERATE RIME ICE WAS EXPECTED IN CLOUDS & PRECIPITATION ABOVE THAT ALT. MODERATE TURBULENCE WAS FORCASTED BELOW 5000 FT NEAR ROUGH TERRAIN. THE PLT HAD ONLY FLOWN THIS ACFT ABOUT 15 HRS & HAD NO RECENT INSTRUMENT FLT TIME. ALSO, HE HAD LOGGED NO KNOWN FLT TIME DURING THE PREVIOUS 3 MOS. THE PLT WAS PREVIOUSLY TREATED FOR HI BLOOD PRESSURE; HOWEVER, ITS RELATIONSHIP WITH THE ACCIDENT COULD NOT BE DETERMINED. NO PREIMPACT MECHANICAL DISCREPANCIES WERE NOTED.