Clear slots are one of the most important things that storm chasers look for in a supercell that may develop a tornado. But what is a clear slot, how do you find a clear slot in a supercell and what do they mean? The Rear Flank Downdraft is an area of clear skies seen on the opposite side of the downdraft of a supercell thunderstorm. Its a sign that rotation is high from the thunderstorm at ground level all the way up to the upper levels. Its a sign that tornado development may be immanent.