THE PLT RCVD A PREFLT BRIEFING BEFORE A MORNING DEP FM MONTEREY. AT THAT TIME, THE FORECAST WAS FOR 3000' TO 5000' BROKEN CLOUDS WITH WIDELY SCATTERED RAIN SHOWERS BY 1600 & WITH A GEN OUTLOOK OF VFR. THE PLT FLEW TO SANTA BARBARA TO ATTEND A MEETING & DEPD SANTA BARBARA AT 1709 FOR THE RTRN TRIP W/O OBTAINING A PREFLT WX BRIEFING. WHEN THE ACFT DEPD ON THE NGT X-COUNTRY FLT, WX CONDS EN ROUTE WERE 2500' TO 5000' BROKEN TO OVERCAST WITH TOPS RPRTD TO 8500' & FLT PRE- CAUTIONS FOR MTN OBSCUREMENT. SUBSEQUENTLY, THE ACFT IMPACTED RISING TERRAIN NEAR THE TOP OF A HILL AT AN ELEV OF APRX 2700' MSL. THERE WAS EVIDENCE THE ACFT WAS IN LVL FLT WHEN THE ACDNT OCCURRED. IMPACT WAS APRX 200 YDS FROM A 2-LANE HIWAY. PERSONS IN THE AREA RPRTD THE WX CONDS CONSISTED OF A LOW OVERCAST, VIS APRX 1/2 MI WITH FOG & LGT RAIN. NO PREIMPACT MECHANICAL PROBLEMS WERE EVIDENT.