AT ABOUT 1005 MST THE PLT RECEIVED A WX BRIEFING FOR A FLT TO FLORIDA WITH AN OVERNIGHT STAY IN TEXAS. THUNDERSTORM ACTIVITY WAS FORECAST ALONG THE PROPOSED ROUTE OF FLT. THE BRIEFER ADVISED THE PLT TO GET AN UPDATED BRIEFING BEFORE DEPARTURE BECAUSE OF THE DEVELOPING THUNDERSTORM ACTIVITY & TO USE THE SERVICES OF ENROUTE FLIGHT WATCH OUTLETS IN OBTAINING PIREP INFORMATION. AT 2045 THE PLT CONTACTED PHOENIX TRACON & STATED HIS INTENTION TO LAND AT PHOENIX. THE PLT INDICATED HE WAS IN THE CLOUDS AT 17,500 FT. RADIO & RADAR CONTACT WAS LOST AT 2049. THE WRECKAGE WAS FOUND APPROXIMATELY 28 MI WNW OF LUKE AFB. PORTIONS OF BOTH WINGS WERE LOCATED 3 MI FROM THE WRECKAGE. THE ABOVE WX IS THE 2055 OBSERVATION AT LUKE AFB. THE SHERIFF'S DEPUTY DISPATCHED TO THE SCENE REPORTED STRONG WINDS & HEAVY ELECTRICAL STORMS IN THE AREA. A HELICOPTER PLT ESTIMATED A CEILING OF 1,500 FT OVERCAST.