Local variables will not be seen by the output routines. You will need to declare the variables you would like to see in the wrfout file as state variables in the Registry. Then these variables will become available to solve_em.F, which calls microphysics_driver. You will need to pass the new variables down to the driver, and then down to the physics scheme called in the driver. These state variables should be declared as 'OUT' variables, and dimensioned by patch dimensions (ime,jme). You then need to fill these arrays with the fields you need to output. Take a look at this talk given at our WRF Tutorial, where you may find some more useful information: