AN MD80 CREW RPTS HAVING TO TAKE EVASIVE ACTION GAR DUE TO WX FACTORS WINDSHEAR AT LGA.

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ACR FLT AHEAD RPTED WINDSHEAR ALERT AT 400 FT AND STARTED MISSED APCH. ATC ASKED OUR INTENTIONS AND WE ADVISED WE WOULD CONTINUE APCH AND MONITOR SIT. WE BROKE OUT OF THE BASES AT 1000 FT MSL TO CLR VMC AND GOOD VISIBILITY BELOW. RWY 22 IN SIGHT AT 1000 FT MSL. AT APPROX 900 FT; FO SAW RAPID 15-20 KT AIRSPD LOSS AND ADVISED CAPT WHO IMMEDIATELY BEGAN MISSED APCH AND PWR ADVANCE. APPROX 3-4 SECONDS LATER; WINDSHEAR ADVISORY FROM RADAR WENT OFF (SOUNDED). SIMULTANEOUSLY WE ENTERED A STRONG UPDRAFT WHICH PEGGED THE VS1 AT 6000 FPM. CAPT INITIATED LEVEL OFF TO STOP AT 2700 FT BUT; DUE TO UPDRAFT STRENGTH; WE FINALLY LEVELED AT 4350 FT WITH VERY PRONOUNCED NOSE DOWN PITCH AND APPROX 1.67 EPR. AIRSPD STABLE AT 200 KTS. AS WE ASCENDED ON GAR; I ADVISED ATC OF OUR INABILITY TO STOP CLB AND CTLR PROGRESSIVELY CLRED US TO 3000-4000 FT; '5000 OR 6000 FT WHATEVER WE NEEDED.' GREAT COORD ON CTLR'S PART TO GET US OUT OF THE AREA AND TO A SAFE HOLDING POS. THERE WAS LITTLE TURB ASSOCIATED WITH THE WINDSHEAR AFTER INITIAL AIRSPD LOSS. VERT RATE ASSOCIATED WITH UPDRAFT WAS VERY IMPRESSIVE! WE DID EXPERIENCE 1 SHEAR REVERSAL AT APPROX 3600 FT THEN BACK UP. ON FINAL APCH; HEADING TO MAINTAIN TRACK WAS APPROX 225 DEGS; TWR ISSUED WINDSHEAR ALERT WITH WINDS 300 DEGS 15 KTS TO 320 DEGS 19 KTS WITH RADIO SWING OF ALL WINDS TO APPROX 330 DEGS 20 KTS. THESE WINDS WERE NOT REFLECTED UNTIL APPROX 900 FT MSL WHEN AIRSPD LOSS OBSERVED.