DRG A WX BRIEFING BEFORE TAKEOFF, THE PLT WAS ADZD OF ICE PELLETS, CLEAR ICING & MODERATE TO SEVERE TURBC IN WESTERN PENNSYLVANIA. AFTER TAKEOFF, HE OBTAINED AN IFR CLNC AT 1144 EST & WAS EVENTUALLY CLRD TO CLIMB TO 13,000'. THE PLT INQUIRED ABOUT THE CLOUD TOPS & WAS ADZD THEY WERE IN EXCESS OF FL 280. AT 1202 EST, WHILE CLIMBING THRU APRX 11,800', THE PLT REQUESTED CLNC TO RETURN TO THE DEPARTURE ARPT. HE WAS CLRD TO TURN TO 090 DEG, WHILE ATC WAS COORDINATING AN IFR CLNC BACK TO THE ARPT. AT 1203 EST, THE PLT WAS ASKED IF HE WAS HAVING ANY DIFFICULTY & HE REPLIED THAT HE WAS PICKING UP ICE & WAS HAVING A PROBLEM WITH HIS ATTITUDE INDICATOR. AT APRX 1204, THE PLT WAS GIVEN A FREQ CHANGE, & SHORTLY THEREAFTER, RADIO & RADAR CONTACT WERE LOST. BEFORE THE ACFT CRASHED, A WITNESS SAW IT TUMBLING WITH ONE WING MISSING. THE LEFT WING & PIECES OF THE EMPENNAGE WERE FOUND APRX 1/2 TO 1-1/4 MI FROM THE WRECKAGE WITH EVIDENCE OF POSITIVE OVERLOAD.