IMC IN VFR FLT.

Narrative

FLT WAS PLANNED BTWN MANCHESTER AND STEWART FIELD; NEWBURGH; NY. FULL WX BRIEFING WAS OBTAINED ON FRI EVENING AND AGAIN SAT AM FROM PORTLAND; ME; FSS. WX DESCRIBED AS VFR WITH CONDITIONS IMPROVING THROUGHOUT SAT. DEPARTED MHT APPROX XA00Z SAT IN VFR; VISIBILITY ABOUT 14 MI; WITH RAGGED BASES TO THE W. CONDITIONS WERE DEFINITELY MARGINAL VMC. I RPTED A VFR CLB FROM 2500 TO 4500 FT MSL TO MHT DEP. HOWEVER; IT BECAME OBVIOUS THAT AN ADDITIONAL CLB TO 6500 WOULD SOON BE REQUIRED TO REMAIN VFR; AS THERE WERE BUILDING TOPS ABOUT 10 MI W OF MY POS. I INFORMED MHT DEP OF MY INTENT; BUT WAS ADVISED NOT TO CLB FROM 4500 TO 6500 AS THERE WAS IFR TFC 500 ABOVE; OPPOSITE (AT 5000) DIRECTION. CONSEQUENTLY; I WAS FORCED TO FLY INTO A SERIES OF CLOUDS AT 4500 FT TO MAINTAIN SEPARATION. I FLEW IN IMC FOR ABOUT 1 MIN BEFORE BREAKING INTO VMC AND CLBING TO 6500 FT. THE REMAINDER OF THE FLT WAS CONDUCTED WITHOUT INCIDENT. WX CONSIDERABLY POORER THAN FORECAST WAS THE MAIN FACTOR FOR THIS INCIDENT; COUPLED WITH A VERY LATE WARNING FROM DEP CTL CONCERNING THE TFC. I HAD REQUESTED AND RECEIVED A STAGE III CLRNC; WAS IN RADAR CONTACT; AND IN CONSTANT COM WITH DEP. CORRECTIVE ACTION IN THIS CASE INVOLVED A DECISION TO PROCEED INTO IMC FOR A SHORT PERIOD TO DEFINITELY AVOID RPTED TFC I COULD NOT VISUALLY DETECT. CONCERNING HUMAN FACTORS; I WAS WELL RESTED PRIOR TO THE FLT AND IN GOOD HEALTH. I REGULARLY FLY THIS PARTICULAR ACFT AND AM INST CURRENT. AS A FLT INSTRUCTOR; I STRESS THE IMPORTANCE OF FULL WX BRIEFINGS; HOWEVER; ON THIS DAY; THE WX WAS FAR WORSE THAN PREDICTED. THE PARTICULAR FLT SHOULD HAVE BEEN CONDUCTED UNDER IFR. I CONSEQUENTLY REQUESTED AND RECEIVED AN IFR RTE FROM ATC WHILE AIRBORNE EVEN THOUGH ENRTE CONDITIONS WERE VFR.