ACR MLG MAKES A CIRCLING APCH TO PHF IN WX RPTED BELOW COMPANY CIRCLING MINS.

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I WAS THE CAPT OF FLT FROM PITTSBURG TO NEWPORT NEWS. THE WX AT NEWPORT NEWS WAS RPTED AT 800 BROKEN; 2 1/2 MI IN FOG; 73 DEGS; AND THE WIND WAS 220 DEGS AT 6 KTS WITH TSTMS N AND E OF THE ARPT. THE NDB APCH TO RWY 20 WAS IN USE AND RWY 7/25 WAS CLOSED. DUE TO THE ERRATIC BEHAVIOR OF THE ADF NEEDLE; APCH CTL WAS ASKED TO CONFIRM MY POS AND GIVE HDG VECTORS FOR PROPER ALIGNMENT. RWY 20 WAS 'IN SIGHT' WELL ABOVE THE RPTED WX; HOWEVER; DUE TO MY ALT AND RWY LENGTH; I DECIDED TO MISS THE APCH AND ASKED FOR A VISUAL MANEUVER. THIS WAS CONFIRMED. THE DECISION TO MAKE A VISUAL MANEUVER WAS BASED ON THE ERRATIC BEHAVIOR OF THE ADF NEEDLE AND THE ACTUAL WX VERSUS THE RPTED WX. THE VISUAL APCH WAS PERFORMED IN A SAFE MANNER AND A NORMAL LNDG WAS ACCOMPLISHED. COMPANY OP SPECS REQUIRE A CIRCLING MIN OF 1000 FT AND 3 MI. THE ACTUAL WX WAS 1000 VARIABLE 800 FT WITH GOOD VISIBILITY. FOR REASONS OF SAFETY AND WITH GOOD VISUAL CONTACT WITH THE RWY; I DECIDED TO PERFORM A SAFE VISUAL APCH INSTEAD OF RETURNING TO TURBULENT IFR CONDITIONS WITH AN ERRATIC ADF NEEDLE.