Instability may be present by lifting air from the surface and throughout the troposphere. The amount of instability present through this process is known as CAPE (Convective Available Potential Energy). This CAPE region is also known as positive area and it is where the theoretical rising parcel of air is warmer than the surrounding environmental air. Being warmer means it is also less dense and will rise freely like a helium balloon due to positive buoyancy. Lifting though does NOT have to be just initiated from the surface. The lifting can begin at any level within the lower troposphere. Because lifting can occur at a variety of different pressure levels, the amount of CAPE that is actualized for a given situation will depend on where the lifting starts from. Meteorologists have developed strategies to deal with this problem in order to get a better sense of how much instability or CAPE will be realized in a given atmospheric set-up. One of these is called Most Unstable CAPE. To get this value, first it is determined how much CAPE is present when air is lifted from a variety of different pressure levels between the surface and about 700 millibars. For example, one parcel will be lifted from the surface, another from 975 mb, another from 950 mb, etc. Each of these situations will have a unique CAPE and these CAPES will vary in magnitudes. The Most Unstable CAPE picks the highest of these values. The image below shows an example of Most Unstable CAPE. Very high instability values exist over Oklahoma and Arkansas on this example.