THE PLT TOOK OFF AT 1125 EST AFTER RECEIVING A WX BRIEFING. WHILE EN ROUTE, THE FORECAST WX FOR THE DESTN BCM WORSE & A SIGMET (1E) WAS ISSUED. AT 1444, THE PLT CONTACTED FT WAYNE FSS & HAD HIS VFR FLT PLAN EXTNDD 1 HR. HE NEITHER REQUESTEDNOR RECEIVED UPDATED WX INFO, WHICH INCLUDED FLT PRECAUTIONS FOR ICING, TURBC & THUNDERSTORMS. AT APRX 1500, BFR IMPACT,THE ACFT WAS SEEN COMING OUT OF A SNOW STORM IN AN UNCONTROLLED DSCNT. THE WRECKAGE WAS SCATTERED OVR AN AREA APRX 1-1/2MI LONG. AN EXAM REVEALED THE L WING, L HORIZONTAL STABILIZER & RUDDER HAD SEPARATED FROM OVERLOAD FAILURE. THERE WAS EVIDENCE THE L WING HAD FAILED UPWARD & STRUCK THE EMPENNAGE DRG SEPN. NO PRE-ACDNT FAILURE/MALFUNCTION WAS FND. ACCORD-ING TO AVAILABLE WX INFO, CLD BASES AT THE ACDNT SITE WERE 2000' MSL (APRX 1100' AGL), TOPS AT 10,000' MSL, VIS ZERO IN CLDS & GREATER THAN 3 MI BELOW CLDS IN SNW SHWRS, FRZG LVL NEAR 3000', MOD TO SVR TURBC BELOW 4000', MOD TO SVR ICING ININ CLDS & IN PRECIP ABOVE THE FRZG LVL.