One relatively easy approach is to write wrfout file in GRIB format, then ungrib these wrfout files and produce initial and boundary conditions for a new WRF run. However, the capability to output wrfout files in GRIB format is broken and I I don't think it is our top priority to fix this issue. An alternative approach is to run UPP to convert wrfout files from netCDF to GRIB.
UPP information can be found
here.
Hope this is helpful for you.