GA SMA VFR IN IMC AND UNAUTHORIZED PENETRATION OF AIRSPACE.

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FLT FROM MUU TO N67 (BOTH LOCATIONS IN PA). PLT CONTACTED FSS FOR COMPLETE WX BRIEFING APPROX 3 HRS BEFORE FLT. GENERAL OUTLOOK WAS GOOD EXCEPT OCCASIONAL TO MODERATE LOW LEVEL TURB PREDICTED. ENRTE WX WAS FORECASTED TO BE 3000-5000 BROKEN AND WAS ESTIMATED TO BE SCATTERED LAYERS AT DEST. DUE TO TURB AT DEP; IT WAS DECIDED TO CLB ABOVE CLOUDS TO 5500 FT DIRECT RAVINE VOR. APPROX 20 MI BEFORE RAVINE; CLOUDS STARTED TO CLOSE UP. AT 10 MI OUT IT WAS SOLID OVCST. PLT CONTINUED ON COURSE; BUT DECIDED TO TURN 180 DEGS AND RETURN TO A BROKEN AREA TO GO DOWN BELOW THE CLOUDS. THIS AREA IS MOUNTAINOUS; BUT PLT IS FAMILIAR WITH TERRAIN. AT TIMES; PLT WAS JUST BARELY REMAINING LEGAL OVER THE MOUNTAINS AT 500 AGL. ONCE REACHING RAVINE VOR; TUNED INTO POTTSTOWN VOR IN TURBULENT CONDITIONS. WITHIN A FEW MINS; IT WAS EVIDENT WE WERE INVOLVED IN A MAGNETIC ANOMALY AND VOR WAS MAKING DRASTIC SWINGS. APPROX 7-8 SM OUT; PLT MAY HAVE FRINGED MUIR AAF CTL ZONE WHICH EXTENDS OUT 7 SM FROM CENTER OF ARPT. PLT CONTINUED FLT FOR APPROX 25 MI AND CONTACTED READING APCH TO PROCEED THROUGH THEIR CTL ZONE AT 2100 FT MSL AS APPROVED AND THEN TO HOME BASE. IN FUTURE THIS PLT WILL CONTACT WX FSS CLOSER TO FLT TIME. ENRTE FSS 122.00 DID NOT RESPOND.