Good evening,
I am not familiar enough with grads to tell you how to make charts with it. But you can use this command to export the variables.
Code:
ncdump -h your_wrf_output_file.nc >> variables.txt
This uses ncdump which is a part of netcdf-bin package on apt.
You can install it using this command in the terminal
if you need to install it using sudo do this command
Code:
sudo apt install netcdf-bin