AFTER RECEIVING HIS PREFLIGHT WX BRIEFING AT 0715 HRS, THE PLT TOOKOFF AT 1436 HRS ON A X-COUNTRY FLIGHT. THERE IS NO EVIDENCE THAT THE PILOT REQUESTED OR RECEIVED A CURRENT WX BRIEFING PRIOR TO THE ACCIDENT. AFTER THE ACFT WAS PROVIDED FLIGHT FOLLOWING INSTRUCTIONS THROUGH AN ARSA THE CONTROLLER INSTRUCTED THE PLT TO RESUME HIS OWN NAVIGATION AND APPROVED HIS CLIMB TO 4,500 FT MSL. THE CONTROLLER OBSERVED THE ACFT'S TARGET ENTER INTO AN AREA OF MOUNTAINOUS TERRAIN AND ASKED THE PLT IF HE SAW THE HILLS. THE PLT REPLIED THAT HE SAW SOME OF THEM. RADIO AND RADAR CONTACT WAS THEN LOST. THE ACFT'S WRECKAGE WAS FOUND ON FEB 14, 1987. WX IN THE AREA AT THE TIME OF THE OCCURRENCE WAS REPORTED AS: SKY PARTIALLY OBSCURED, ESTIMATED CEILING BROKEN AT 2,200 FEET MSL, OVERCAST SKY AT 5,000 FEET MSL, VISIBILITY 6 MILE, TEMPERATURE 67 DEGREES, DEW POINT 57 DEGREES FAHRENHEIT, WIND FROM 220 DEGREES AT 5 KNOTS, ALTIMETER 30.10 'HG. THE PLTS FLT LOG WAS NEVER LOCATED. HIS INSTRUMENT CERT EXPIRED IN 1982.