A second-order-closure approach is used to model the behavior of the turbulent convection current in an unstable planetary boundary layer over horizontally uniform terrain. The model identifies the surface fluxes of heat and momentum and the height of the inversion capping the layer as the primary meteorological parameters determining the strength of this current. Results indicate that convection of charge supplied by the electrode effect can have a significant impact on the local atmospheric electric circuit. A sample calculation for a very unstable layer shows that convection currents act as a local generator capable of reducing the total downward current density by as much as 44%.