DURING A WX BRIEFING THE PILOT WAS ADVISED THAT VFR FLT WAS NOT RECOMMENDED. WHILE ENROUTE TO COLUMBIA THE PILOT CALLED ATC REQUESTING WX INFO. THE CONTROLLER OBSERVED THE AIRPLANE ENTERING POSITIVE CONTROL AIRSPACE AND TOLD THE PLT TO REMAIN BELOW 18,000 FT. THE PLT TOLD THE CONTROLLER THAT IT WAS NECESSARY TO CLIMB ABOVE FL 180 TO REMAIN VFR. THE CONTROLLER ADVSD THE PLT TO CONTACT EDWARDS RAPCON IF HE REQUESTED ANY IFR ASSISTANCE. THE AIRPLANE'S MODE C TRANSPONDER WAS TRACKED FOR OVER AN HOUR BETWEEN FL 196 AND 14,300 FEET. THERE WERE NO FURTHER COMMUNICATIONS WITH THE PLT. RADAR CONTACT WAS LOST AT 1709 - ABT 1 HOUR 9 MIN AFTER INITIAL CONTACT WITH THE PLT. THE ACFT WAS FOUND IN A MOUNTAINOUS AREA 7 MONTHS LATER AT 11,300 FT MSL. THE AIRPLANE WAS NOT EQUIPPED WITH SUPPLEMENTAL OXYGEN. FORECASTED WX INDICATED MODERATE TO HEAVY RAIN WITH A WINTER STORM WARNING FOR HIGHER ELEVATIONS WITH POSSIBLE ACCUMULATIONS OF 2-3 FT OF SNOW, WINDS GUSTING TO 50 MPH AT HIGHER ELEVATIONS.