ON XCOUNTRY FERRY OF SMA ACFT PF VFR ON TOP REACHED 12500 ON TOP OF ICING CONDITIONS. OBTAINED CLRNC FOR DSCNT DOWN THROUGH; ICED UP WITH RIME; DECLARED EMER FOR DSCNT BELOW MIN ENRTE; BROKE OUT; LANDED MGW.

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I WAS FERRYING AN SMA FROM HARRISBURG; PA; TO NORMA; OK. I DEPARTED HARRISBURG; PA; VFR. IT SOON WAS VFR ON TOP OF AN OVCST LAYER ABOUT 3000 FT ON TOP. MY FIRST STOP WAS GOING TO BE LEXINGTON; KY. IT SOON GOT DARK AND THE TOPS OF THE OVCST LAYER ROSE TO AN ALT WHICH WOULDN'T ALLOW ME TO MAINTAIN VFR. RPTS THAT I RECEIVED FROM TWEB CALLED FOR MODERATE TO SEVERE ICING FROM THE SURFACE TO MY ALT WHICH WAS NOW 12500 FT MSL. I HAD TO MAKE A DECISION TO TURN BACK OR LAND AND RISK ICING CONDITIONS. I HAD 2 HRS OF FUEL ON BOARD AND COULD NOT REMAIN AT MY PRESENT ALT WITHOUT OXYGEN. I MADE THE DECISION TO GET CLRNC TO THE NEAREST ARPT WITH AN ILS. I DID NOT HAVE APCH PROCS FOR ANY ARPT BUT MY DEST THAT I HAD PLANNED FOR AN IFR INTO. MY DEST WAS IN BETTER CONDITIONS THAN MY ALTERNATE FOR WHICH I FACED NOW. MORGANTOWN WAS VFR AND CLOSE. I WAS CLRED TO 8000 AND THEN 3000 AT PLT'S DISCRETION TO MY NEW ALTERNATE. I STARTED A RAPID DSCNT WHERE I PICKED UP MODERATE RIME. AT 3000 I WAS STILL IMC AND PICKING UP ICE (3000 WAS MIN VECTORING ALT). I DECLARED AN EMER FOR A LOWER ALT WHERE I KNEW I WOULD BREAK OUT BECAUSE MORGANTOWN WAS VFR. THEY GAVE ME 2400 WHERE I BROKE OUT AND SAW THE ARPT. I SHOULD NOT HAVE ASSUMED I COULD FLY TO MY DEST VFR ON TOP WITHOUT MORE ADEQUATE PIREPS FOR MY ENRTE PORTION.