THE FLT HAD DEPARTED TUCSON, AZ, ON A SPECIAL VFR FERRY FLIGHT TO GREYBULL, WY. THE AIRPLANE WAS NOT INSTRUMENTED FOR IFR FLIGHT. WHEN THE FLT REPORTED OVER WINSLOW, IT WAS ADVISED THAT VFR FLT WAS NOT RECOMMENDED NORTHBOUND FROM ITS PRESENT POSITION. SURFACE WX CONDITIONS IN SOUTHCENTRAL WYOMING/NORTHWESTERN COLORADO AT THE TIME OF THE ACCIDENT WERE CONSISTENT WITH LOW CEILINGS, CLOUDS AND SNOW AS REPORTED BY WITNESSES AND SURFACE WX OBSERVATIONS. THE WITNESSES, LOCATED NEAR THE DIXON ARPT, REPORTED HEARING A LOW FLYING AIRCRAFT TRAVELLING W TO E, AND ANOTHER WITNESS NE OF THE ARPT HEARD AN AIRCRAFT 'REVVING' ITS ENGINES. RADAR DATA SHOWS THE AIRCRAFT TRACKING NORTHBOUND SLIGHTLY EAST OF THE DIXON ARPT, AND EXECUTING A CLOCKWISE 360 DEG TURN NE OF THE ARPT AND IN THE VICINITY OF ONE OF THE WITNESSES. THE LAST RADAR TARGET RECEIVED PLACED THE AIRCRAFT APRX 1 MI NNE OF THE ACCIDENT SITE. THE AIRCRAFT IMPACTED SNOW COVERED TERRAIN IN A STEEP NOSE-DOWN ATTITUDE.