LAX87FA134

Before takeoff, the plt was adzd that strong head winds, mod to svr turbc, mtn obscurement, multiple layers of icing & deteriorating wx were forecast along his route of flt. He filed an IFR clnc & took off at 1115 PST. While en route, he reqd the medford wx & was adzd of standing lenticular clouds. At 1328 PST, he canceled his IFR clnc. Later, at 1535, he obtained another IFR clnc & was assigned an alt of 11,000'. At 1546 PST, the plt rprtd he was enctrg downdrafts; 8 min later, he said his alt was 9300'. Shortly, thereafter, radar & radio ctc were lost after the acft dscndd thru 8900'. Subsequently, the acft crashed on the lee side of a 9025' mtn at aprx the 6200' lvl. It was found in a near vertical nose down attitude with its belly against an impact damaged tree. The aft fuselage was bent & twisted about 90 deg, but the empennage was essentially undamaged. No preimpact part failure or malfunction was evident. Aprx 7 mi north at Weed arpt (elev 2938'), the wind gusts were estd at 70 to 75 mph.