Channel mobility is one of the most critical parameters in 4H-SiC based Power MOSFETs and contributes a significant fraction of device on-state resistance (RON). 4H-SiC has a hexagonal crystal structure and the bulk mobility is anisotropic, larger in the (0001) direction (parallel to the a-face or m-face), and lower perpendicular to that (along Si-face directions). Such an anisotropic nature is also observed in channel mobilities when channels are formed along these crystallographic orientations. Experimentally, it has been shown that the a-face channel mobility is much higher compared to the Si-face, making a-face a very attractive option for a wide range of applications in the power electronics market. However, to the best of our knowledge, Technology Computer Aided Design (TCAD) modelling of the a-face channel mobility is missing in the literature. In this paper, we present a well calibrated a-face channel mobility model that shows an excellent match with the available experimental data and further provides critical insights into the anisotropic nature of channel mobility in 4H-SiC MOSFET structures.