THE PILOT RECEIVED NUMEROUS WEATHER BRIEFINGS/UPDATES BEFORE TAKEOFF, WHICH INCLUDED TWO PILOT REPORTS OF WINDSHEAR BY AIRCRAFT ON THE APPROACH INTO APPLETON. SHORTLY AFTER TAKEOFF CONVECTIVE SIGMET 1E WAS TRANSMITTED BY THE RADAR CONTROLLER ON THE SAME FREQUENCY HE WAS WORKING N87163. THIS SIGMET CALLED FOR EMBEDDED THUNDERSTORMS. ABOUT 10 MIN LATER, WHILE BEING VECTORED FOR THE APPROACH INTO APPLETON, THE PILOT WAS GIVEN HEADING DEVIATIONS BECAUSE OF WEATHER. THE AIRCRAFT CRASHED 1/2 MI FROM THE APPROACH END OF THE RUNWAY. A WITNESS WHOSE RESIDENCE IS LOCATED BETWEEN THE OM AND MM FOR THE ILS APPROACH REPORTED A 'HUGE DOWNPOUR' WITH 'VERY STRONG WINDS' AT THE TIME OF THE ACCIDENT. WRECKAGE EXAMINATION REVEALED THAT ALL POWER CONTROLS FOR BOTH ENGINES WERE IN THE FULL FORWARD POSITION, AND THAT THE LEFT AND RIGHT MAIN LANDING GEAR MOUNTING TRUNNIONS WERE DISPLACED UPWARD INTO THE WING FUEL TANKS.