WX AND TURB ENCOUNTER RESULTS IN ALT AND COURSE DEV NEAR LGA; NY.

Narrative

WHILE BEING RADAR VECTORED FOR APCH AT 3000 FT; WE ENCOUNTERED WINDSHEAR THAT RESULTED IN AN INCREASE OF AIRSPD OF +50 KTS FOLLOWED BY LOSS OF 20 KTS. WE EXECUTED AN ESCAPE MANEUVER WHILE HOLDING OUR ASSIGNED ALT AND AIRSPD. MODERATE TO SEVERE TURB WAS ALSO ENCOUNTERED. WE ELECTED TO FLY IN A DIRECTION THAT WOULD TAKE US AWAY FROM THE WX. THIS WAS CONTRADICTORY TO ATC REQUEST. BUT SAFETY TO THE ACFT REQUIRED US TO EXIT THE AREA ASAP. DURING MANEUVERING; A TFC CONFLICT WAS PRESENTED. WE WERE ABLE TO SIGHT THE TFC AND MAINTAIN VISUAL SEPARATION. AT THIS TIME WE WERE ISSUED A HDG AND ATTEMPTED TO COMPLY. DURING THE TURN; A DOWNDRAFT WAS ENCOUNTERED. THE AUTOPLT WAS NOT ABLE TO HOLD ALT AND SUBSEQUENTLY LOST 300 FT. THE AUTOPLT WAS DISENGAGED AND THE ALT WAS REGAINED MANUALLY. DURING THIS TIME; LGA CHANGED ARR RWYS. WE WERE ISSUED VECTORS FOR THE APCH TO RWY 31. WHILE ON DSCNT; THE WX AND TURB IMPROVED AND A SAFE APCH AND LNDG WERE MADE. SUPPLEMENTAL INFO FROM ACN 475815: AFTER LANDING; CALLED N90. INFORMED SUPERVISOR OF WHAT HAPPENED. HE SAID THERE WAS NO LOSS OF SEPARATION AND NO PROB. HE WOULD PASS INFO TO CONTROLLER. LESSON LEARNED: EVEN WITH ROUTINE LANDINGS OCCURRING IN VIS CONDITIONS OVER THE FIELD; SEVERE WEATHER IN A HIGH DENSITY ENVIRONMENT CAN QUICKLY CAUSE TASK SATURATION ON BOTH SIDES.