Hi,
Just to add some more information:
On June the 12th XyGrib switched to using the FV3 version of GFS (v15.1).
The older version is still available on a parallel NOAA server but we are not using it any more.
The new version, being non-hydrostatic, has some new meteorological parameters. The one most applicable for sailing forecasts is "Reflectivity".
The option to download and display reflectivity for GFS has been added in the v1.2.6 release of XyGrib
Please note that zyGrib still exists and it can be found at zygrib.org