Hi,
Errors in metgrid are all related to the netCDF library, and in metgrid, we make direct calls to the netCDF Fortran 90 interface, while we think the WRF netCDF I/O API only uses the netCDF Fortran 77 interface. As long as you are not intending to use the ability to initialize WRF simulations with MPAS output, I've attached a modified file that I hope will help. Place this file in your WPS/metgrid/src directory and then recompile. Let me know if that helps.