The usual way of finding the LFC is to lift a parcel from a lower level along the dry adiabatic lapse rate until it crosses the mixing ratio line of the parcel: this is the lifted condensation level (LCL). From there on, follow the moist adiabatic lapse rate until the temperature of the parcel reaches the air mass temperature, at the equilibrium level (EL). If the temperature of the parcel along the moist adiabat is warmer than the environment on further lift, one has found the LFC.
Since the volume of the parcel is larger than the surrounding air after LFC by the ideal gas law (PV = nRT), it is less dense and becomes buoyant rising until its temperature (in E) crosses back the airmass one. If the airmass has one or many LFC, it is potentially unstable and may lead to convective clouds like cumulus and thunderstorms.
The impact on simulated storm structure and intensity of variations in the mixed layer and moist layer depths
Jul 01, 2002; ABSTRACT The sensitivities of convective storm structure and intensity to variations in the depths of the prestorm mixed layer,...