... in a conditionallyunstable atmosphere over the GreatPlains. Notice that, in the distance, the cumulonimbus with the anvil top hasreached the stable part of the atmosphere. to peer into a tornado-generating ... dense than the air aroundthem, once the parcels start upward, they will continueto rise on their own, away from the surface. Thus, wehave an absolutely unstable atmosphere. The atmosphere ... lingering close to the ground. As the day progresses, sunlight warms the surface and the surface warms the air above. As the air temperature near the ground increases, the lower atmosphere graduallybecomes...