DURING THE 1725 CDT WX BRIEFING THE PLT WAS INFORMED THAT THE KANSAS CITY AREA WOULD BE 1600 FT BROKEN, OCCASSIONAL 800 FT BROKEN, 3/4 MI VISIBILITY WITH THUNDERSTORMS & MODERATE RAIN WITH STRONG SURFACE WINDS ABOUT 35K. THE FORECAST WAS VALID TO 2200 CDT. THE PLT INDICATED HE DID NOT NEED ANY ENROUTE FORECASTS. THE BRIEFER STATED TO THE PLT THAT RADARWAS SHOWING AN AREA OF THUNDERSTORMS & RAIN SHOWERS EXTENDING FROM 70 MI NW OF KANSAS CITY DOWN TO 60 MI NORTH OF KANSAS CITY & FROM THERE ON UP TO FT.DODGE, THE AREA OF THUNDERSTORMS MOVING NE AT 30K. THE PLT DEPARTED OLATHE, KS AT 2000 CDT. A WITNESS HEARD THE SOUNDS OF AN ACFT ENG DECREASING, INCREASING & THEN SILENCE. A WITNESS WHO HEARD THE ACFT PASS BY JUST BEFORE IMPACT STATED THAT THE WX AT THE TIME WAS MODERATE RAIN, APPROXIMATE 1 MI VISIBILITY, & INTERMITTENT LIGHTNING & THUNDER. PORTIONS OF EACH WING & THE HORIZONTAL TAIL SECTION WERE LOCATED APPROXIMATELY 3/8 MI SOUTH OF THE MAIN WRECKAGE.