Analytical solution and numerical results are provided for the problem of plane wave scattering by an electrically large Perfect Electric Conductor plate located vertically over a simple lossy dielectric half-space. The incoming monochromatic homogeneous plane wave is assumed to be incident from an arbitrary direction and decomposed into TE and TM components. Physical Optics approximation is used for estimating the currents induced on the plate. The scattered fields are obtained explicitly by evaluating the Electric Field Integral Equation analytically incorporating the set of Green functions by R. W. P. King which apply under High Contrast Approximation. Amplitude and phase variations of the numerical distance and attenuation function are illustrated in HF-MW band ranges. Azimuth and elevation patterns for scattered electric fields are illustrated with emphasis on the relative contributions of surface wave fields depending on operating frequency and refractivity. An analytical procedure to extract free space RCS information from measured/calculated data is introduced based on the asymptotic behaviors of surface waves and its stability is tested numerically.