Conditional instability refers to an atmospheric state in which the environmental lapse rate lies between the dry adiabatic lapse rate and the saturated (moist) adiabatic lapse rate, so that an air parcel is stable with respect to small, unsaturated (dry adiabatic) displacements but becomes unstable once it is lifted enough to become saturated and cool at the slower moist adiabatic rate, at which point it can become buoyant relative to its surroundings and continue rising freely.
An air parcel displaced vertically initially cools at the dry adiabatic lapse rate (about 9.8 degrees C per km) as long as it remains unsaturated....
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