DESPITE 5 PRE-FLT WX BRIEFINGS FROM THE LOCAL FSS, WARNINGS FROM A PLT WHO HAD JUST LANDED IN A CORPORATE JET, AND QUESTIONING FROM THE ATCT REGARDING THE PLT'S KNOWLEDGE OF EXISTING CONDITIONS. THE PLT DEPARTED AT 1138 EST. THE ACFT IMPACTED INVERTED AND THE WRECKAGE WAS CONSUMED BY POST-CRASH FIRE. THE RIGHT WING SEPARATED FROM THE FUSELAGE ABOUT 3 FT OUT FROM THE ROOT AND WAS FOUND APPX 3/4 MI FROM THE MAIN WRECKAGE. ABOUT 100 FT FROM THE PRIMARY IMPACT POINT THE EMPENNAGE WAS FOUND WITH THE FLT CONTROL SURFACES MISSING. INVESTIGATION REVEALED NO EVIDENCE OF PRE-EXISTING CRACKS OR FATIGUE. THE PLT WAS A DESIGNATED FAA AVIATION MEDICAL EXAMINER. HIS WX BRIEFINGS FORECAST LOW CEILINGS, RAIN, FOG, AND OCCASIONAL SEVERE TURBULENCE BELOW 8,000 FT. CLIMBING TO 6,000 FT THE ACFT REACHED 5,600 FT BEFORE GOING INTO A VERY RAPID DESCENT.