For the practical compression molded glass-mat thermoplastics (GMTs), it is important that the flow pattern in squeezing of circular disks with initial alignment, from manufacturing or prior flow, usually develops into an elliptical shape due to fiber-orientation-induced anisotropic flow. However, prior predictive engineering tools have always provided unsatisfactory isotropic flow results. This challenging anisotropic flow prediction problem has been addressed in this work. Based on the orientation averaged fourth-order viscosity tensor, the Favaloro-Pipes model for an orientation informed isotropic viscosity is proposed and implemented to simulate the natural anisotropic flow behavior in GMT compression molding simulation.