THE PLT (WITH ONLY 13 HRS FLT TIME IN THE HI PERFORMANCE SAILPLANE) TOOK OFF AT 1330 PDT. PSN RPRTS WITH HER GND CREW WERE NORMAL UNTIL 1630, THEN ANOTHER PLT OFFERED TO RELAY MESSAGES. AFTER CTCG HER GND CREW, THE OTR PLT TRIED CALLING HER BACK AT APRX 1645, BUT GOT NO RESPONSE. A SEARCH WAS INITIATED, THE WRECKAGE WAS FND THE NEXT DAY AT 0955, SCATTEREDOVR A WIDE AREA ON MTN/HILLY TRRN. THERE WAS EVIDENCE OF AN IN-FLT BREAKUP. THE RGT WING HAD FAILED AT THE OUTBOARD END OF THE FLAP; THE OUTBOARD PORTION WAS FND APRX 500' WEST OF THE MAIN WRECKAGE. THE LEFT WING HAD FAILED IN THE SAME AREA& ITS MAIN SPAR HAD FAILED AT THE WING ROOT. FRACTURES WERE TYPICAL OF POSITIVE OVERLOAD WITH NO PREEXISTING FATIGUE. HORIZONTAL STABILIZER WAS FND APRX 1/2 MI SOUTH OF THE MAIN WRECKAGE. THERE WAS EVIDENCE THE PLT HAD BAILED OUT, BUT HADHIT THE GND BEFORE THE CHUTE WAS FULLY DEPLOYED. THE CHUTE WAS LAST PACKED ON 2/4/88. TOWERING CUMULUS CLDS WERE RPRTD 34 MI WEST AT LAKE TAHOE. ANOTHER PLT IN THE VCNTY MADE A PRCNTRY LNDG DUE TO TSTM, RAIN, TURBC, & GUSTY WIND.