ALT BUST.

Narrative

I WAS PLTING AN SMA ON IFR PLAN TO TEB. CLRED AT 8000 FT MSL AND PROCEEDING W ON V292 FROM SASHA INTXN. A LARGE BLACK BUILDUP APPEARED AHEAD. I ASKED FOR AND RECEIVED CLRNC TO DEV L (SW) AROUND THE BUILDUP. DURING THIS DEV I WAS REQUESTED AT LEAST TWICE TO RETURN AS SOON AS POSSIBLE TO V292. I REPLIED I WOULD TRY BUT THAT NOW THE BUILD UP WAS ON MY R AND AHEAD OF ME. THEN A SMALLER BUT DARK BUILDUP APPEARED AHEAD BUT I PERCEIVED AN OPENING BTWN THE 2 BUILDUPS AND ADVISED BOS CENTER THAT I WAS TRYING TO RETURN TO V292 THROUGH THE 'OPENING'. SUDDENLY THE ACFT ENTERED A STRONG VERT LIFT. I REDUCED PWR TO ATTEMPT TO MAINTAIN 8000 FT. MY VSI PEGGED AT 2000 FPM CLB. MY ATTITUDE AND REDUCED PWR SHOULD HAVE ACHIEVED 1000 FPM DSCNT. THE RAPID ASCENT WAS ARRESTED AT 9400 FT MSL BUT DSCNT WAS STILL NEGLIGIBLE DESPITE REDUCED PWR AND DSCNT ATTITUDE. I ADVISED BOS CENTER OF THESE EVENTS AND RECEIVED A SOUTHERLY VECTOR. EVENTUALLY I REACHED MVMC AND ADVISED BOS I COULD RETURN TO 8000 FT MSL WHICH CENTER APPROVED AND I COMPLIED. MY MAIN THOUGHT FOR AVOIDING EXPERIENCES OF THIS NATURE IS NOT TO BE PERSUADED BY AN ERNEST OR ANXIOUS CTLR TO HURRY BACK FROM AN APPROVED DEV TO THE ORIGINAL COURSE WHEN THIS INVOLVES RISK AS FLYING BTWN CLOSELY ADJACENT BUILDUPS OR CLOSE TO THEM. THIS IS NOT INTENDED AS CRITICISM OF THE CTLR WHO WAS VERY HELPFUL AFTER I EXPERIENCED THE ALT PROBLEM. IT WOULD HELP IF CENTERS WERE EQUIPPED WITH BETTER WX RADAR.