SMT EXPERIENCES EXTREME DOWNDRAFT; UNABLE HOLD ALT. ALSO HAS SOME ICING DURING FLT.

Narrative

I DEPARTED WINCHESTER; VA ON AN IFR FLT PLAN TO TAYLOR COUNTY; KY. ON CLB OUT I PROCEEDED THROUGH A BROKEN CLOUD LAYER FROM APPROX 4000 TO 5500 FT. I WAS CLRED TO 8000 FT AND EXPERIENCED NO TURB; BUT LIGHT RIME ICE IN THE CLOUDS; BUT L THE ACFT AS SOON AS I BROKE OUT INTO THE SUNLIGHT. WINDS WERE BRIEFED BY MRB FSS TO BE OUT OF THE W AT ABOUT 45. EVERYTHING WAS SMOOTH UNTIL ABOUT 40 W OF LINDEN VOR. I COULD SEE A CLOUD BANK AHEAD; BUT IT DID NOT APPEAR TO BE ANYTHING. I CALLED WASHINGTON CTR AND ASKED FOR 10000 AND WAS CLRED TO 10000. I STARTED TO CLB JUST AS I REACH THIS FIRST CLOUD BANK. AS I WAS CLBING I STARTED TO EXPERIENCE A DOWN DRAFT; BUT WAS ABLE TO CONTINUE TO CLB EVEN THOUGH THE AIRSPD DROPPED OFF TO ABOUT 110 IAS; AS I WENT THROUGH 9000; I ENTERED THE UPDRAFT AND LEVELED AT 10000; MAINTAIN 10000 FT; IAS CONTINUED TO BUILD TO OVER 200 IAS FOR ABOUT 30 SECONDS AND TEN EVERYTHING RETURNED TO NORMAL. CRUISING AT 10000 FT WITH 160 KIAS. AT ABOUT 50 NM W OF LINDEN ABOUT 40 E OF ELKINS; I OBSERVED ANOTHER CLOUD BANK AT MY ALT; I CALLED WASHING CTR AND ASK FOR 12000 FT TO GET ABOVE THIS CLOUD BANK. AS I PASSED THROUGH THESE CLOUD TOPS I WOULD GET A TRACE FOR RIME ICE AND DID NOT WANT TO STAY IN THE CLOUDS FOR A PROLONGED PERIOD OF TIME. AS CTR FINALLY CLRED ME TO 12000 FT I WAS GETTING OVER CLOSE TO THIS CLOUD BANK. I STARTED THE CLB BUT AT THE TIME MUST HAVE HIT THE SECOND DOWNDRAFT. MY IAS STARTED DROPPING AND TO MAINTAIN 10000 I WAS BELOW 100 IAS; MY IAS STARTED DROPPING FURTHER AND THE STALL WARNING SOUNDED. AT THIS TIME THE ACFT STARTED DSNDING. I APPLIED MAX PWR; MAX RPM AND TRYING TO MAINTAIN LEVEL FLT WITH IAS ABOVE THE STALL; I MAINTAINED CTL MY ALT WAS DOWN TO ABOUT 9300 FT; CTR CALL AND ASKED ABOUT ALT; I ADVISED HIM OF MY DIFFICULTY AND REQUESTED 8000 FT. I FELT THAT I COULD MAINTAIN 8000. I CONTINUED MY DSCNT TO 8000 AND AFTER A MIN OR SO; BROKE OUT IN THE CLR. I CONTINUED MY FLT ON TO TAYLOR CO. WITH NO FURTHER INCIDENT. WASHINGTON CTR CALLED ME AND I EXPLAINED WHAT HAD HAPPENED TO ME. I HAVE NEVER ENCOUNTERED THAT SEVERE OF A MOUNTAIN WAVE OR DOWNDRAFT IN THAT AREA IN MY FLYING EXPERIENCE. THAT THE FACT COULD NOT FLY OUT OF. I FEEL THAT THE WX BRIEFING I RECEIVED WAS EXCELLENT; AND THIS INCIDENT WOULD BE VERY HARD TO PREDICT.