THE FLT WAS CLEARED TO MAINTAIN 3,000 FT MSL UNTIL OVER THE ARPT, THEN CRUISE. THE PLT HAD PREVIOUSLY STATED THAT HE COULD SEE THE LIGHTS ON THE GROUND & THAT HE WAS 15 MI FROM THE ARPT. AT 2013 THE PLT STATED "WE OUGHTA BE ABLE TO CANCEL HERE." THE ACFT WOULD HAVE BEEN ABOUT 6 MI FROM THE ARPT. THE ARPT OPERATOR HEARD AN ACFT LOW OVERHEAD & WAS ABLETO SEE STARS. OTHER GROUND WITNESSES CLOSER TO THE POINT OF IMPACT OBSERVED VERY THICK PATCHY FOG WITH VISIBILITY ABOUT 200 FT. ONE WITNESS OBSERVED THE ACFT NAVIGATION LIGHTS DO SOME UNUSUAL MANEUVERING, WHILE ANOTHER WITNESS SAW THE LIGHTS VERY LOW. THE ACFT IMPACTED THE GROUND IN A LEFT WING LOW, NEAR LEVEL FLIGHT ATTITUDE. THE WRECKAGE WAS CO-LOCATED WITH AN APPROXIMATE DOWNWIND TO BASE LEG TURN. THERE IS A SINGLE VOR/DME APCH TO RWY 11. THE MDA IS 1,260 FT & REQUIRES A MINIMUM VISIBILITY OF 1 MI. THE CIRCLING APCH HAS AN MDA OF 1,420 FT & ALSO REQUIRES A MINIMUM VISIBILITY OF 1 MI. THE PLT HAD RECEIVED AN ALTIMETER SETTING OF 29.77. THE ACFT'S ALTIMETER WAS SET BETWEEN 30.29 & 30.30.