AT 0112 CST, THE PLT TELEPHONED THE FSS & REQUESTED A WX OUTLOOK FOR A 0600 CST DEPARTURE. THE WX BRIEFER ADZD THE WX TO THE SOUTH WAS DETERIORATING & THAT THE DESTN WOULD BE IFR BY ABOUT THE PLANNED DEPARTURE TIME. ALSO, THE BRIEFER SUGGESTED THE PLT COULD DELAY HIS FLT AS A SLOW IMPROVEMENT WAS EXPECTED. AT ABOUT 0130 TO 0200 CST, THE PLT TOOK OFF. DURING ARRIVAL, HE SAW THE ARPT BEACON & CONTD. HOWEVER, THE ACFT SUBSEQUENTLY CRASHED ABOUT 1000' SOUTH OF RWY 9, NEAR THE DEP END. DUE TO HIS INJURIES, THE PLT COULD NOT REMEMBER THE OCCURRENCE. A POLICE OFFICER, WHO RESPONDED TO THE ACDNT, SAID HE HAD TO LIMIT HIS SPEED TO APRX 30 TO 35 MPH DUE TO HVY GROUND FOG. AN EXAM REVEALED THAT DURING IMPACT THE NOSE & LEFT MAIN GEAR COLLAPSED; THE PROP, ENG COMPARTMENT, & BOTH WING TIPS WERE DAMAGED; & THE AFT FUSELAGE WAS BROKEN & BENT DOWNWARD BEHIND THE WINGS & CABIN AREA. ABOUT 45 MI SSE AT EAU CLAIRE, WI, THE 2251 CST WX WAS IN PART: 400' OBSCURED, VIS 1.5 MI WITH FOG & DRIZZLE.