The cloud base is the elevation above the ground in which the bottom of the cloud is found. Often cloud bases look fairly flat since they are being looked at from a distance and the cloud base starts at about the same elevation near a particular region of cloud. A lowered or lowering cloud base is often in reference to one portion of a thunderstorm having clouds that are closer to the ground surface. A thunderstorm has an updraft and a downdraft region. It is the updraft region in which the lowered cloud base will typically be found. The cloud base tends to be lower in the updraft region because this is the region that has rising air and this is the region that is experiencing moisture convergence. Air that has a high relative humidity and rises will not have to rise too far before becoming saturated. Once the air becomes saturated then clouds will develop as the air continues to rise. The diagram below shows a thunderstorm with a lowered cloud base. This lowered cloud base region is where air is rising into the thunderstorm (updraft region).