The CISL Data Archive hosted by NCAR contains North American Regional Reanalysis files which may be used for WRF in place of other types of data, such as GFS. These files may be downloaded at CISL RSA: ds608.0 Downloads.
After logging into the website, clicking Data Access will bring up a portion of the site where you may search for NARR files based on date. Using the “regrouped 3-hourly files” link, you may download the necessary files needed for metgrid.exe to run correctly. These are the 3D, sfc and flx files. You will also need the correct variable table.
There are three programs you can use in tandem to generate all of the met_em* files. These scrips can be transfered from /center/d/VOLCWRF/sde/scripts/NARRmetgrid/ into your WPS main directory. The variable table you need is located in this directory as well, and should be moved to the ./WPS/ungrib/Variable_Tables/ directory. Upon downloading the 3D, slc, flx and fixed field files from the CISL website, extract the files into ./WPS/NARR/3D, ./WPS/NARR/slc, ./WPS/NARR/flx and ./WPS/NARR directories, respectively. If you do this, you may then run ./runAll.sh and this will generate the met_em* files you need.