Take a look at a real rotary snow plow. The center has a cone with two or three heavy "sticks" or bars (1 inch square or more and 8 or 10 inches long) sticking out at a right-angle near the tip of the cone that break up the snow right in the center and move it toward the impeller blades. At the corners, especially the bottom two, there is a curved ramp that guides the snow to the impeller to get tossed out instead of building up against the flat face of the housing.