THE PILOT WAS FLYING ONE OF SIX AIRCRAFT THAT ATTEMPTED TO FLY THROUGH THE MOUNTAIN PASS IN RAPIDLY VARYING INCLEMENT WEATHER CONDITIONS. THE AIRCRAFT IMPACTED TERRAIN NEAR THE BOTTOM OF THE PASS WHILE THE PILOT WAS MANEUVERING TO REVERSE COURSE. PERSONS ARRIVING AT THE SCENE SHORTLY AFTER THE ACCIDENT DESCRIBED FOG AND LOW CEILINGS IN THE PASS THAT WERE RAPIDLY VARYING, WITH BASES OF CLOUDS AS LOW AS A HUNDRED FEET OR SO ABOVE THE CRASH SITE.