WW3/https://www.glerl.noaa.gov/emf/waves/nomads_Grib_Depot/

The latest file is called nomads.grib2 and is overwritten 4x per day (@01:40, 07:40, 13:40, 19:40 GMT). 
It is approximately 122MB.
The file inventory descriptor is called nomads.grib2.idx.

Here are the links and description for the NCEP WWIII data:

https://nomads.ncep.noaa.gov/

Under Ocean Models:Great Lakes Wave:
https://nomads.ncep.noaa.gov/txt_descriptions/GLWave_model_forecast_doc.shtml
The Great Lakes Wave Unstructured (GLWU) system provides wave guidance to the National Weather Service (NWS) Great 
Lakes region Weather Forecast Offices, and to the general public, using an implementation of the wave modeling 
framework WAVEWATCH III. The GLWU is implemented on an unstructured grid with resolution ranging from 2.5km in 
deep waters to 250m near the coast. The system runs 24 daily cycles, 20 of which provide short-range forecasts 
out to 48h, and 4 (01Z, 07Z, 13Z and 19Z) provide longer-range forecasts out to 149h.

https://nomads.ncep.noaa.gov/pub/data/nccf/com/wave/prod/
glwu: https://nomads.ncep.noaa.gov/pub/data/nccf/com/wave/prod/glwu.20210727/
e.g.,
https://nomads.ncep.noaa.gov/pub/data/nccf/com/wave/prod/glwu.20210727/glwu.grlc_2p5km.t01z.grib2.idx
https://nomads.ncep.noaa.gov/pub/data/nccf/com/wave/prod/glwu.20210727/glwu.grlc_2p5km.t01z.grib2

#2.5km Lambert Conformal Grid - Regional Great Lakes Wave Model
#NDFD Wind Forcing    Filename    Inventory
#     glwu.grlc_2p5km.tCCz.grib2    FH00-149
#     #https://www.nco.ncep.noaa.gov/pmb/products/wave/
#Times in GMT

Addition source of grib2 files for the Great Lakes:
1) Numerical data from the RDWPS in GRIB2 format (wind and waves)
https://weather.gc.ca/grib/grib2_RDWPS_e.html

2) U.S. National Ice Center (Ice concentration)
https://usicecenter.gov/Products/GreatLakesData

3) Squid Marine Weather Software and data
http://lakeeriewx.com/CaseStudies/SquidSailing/SquidSailing.html

4) Free Grib Files from GMN Marine Weather Services (wind and waves)
http://www.globalmarinenet.com/free-grib-file-downloads/

5) Pivotel Free GRIB Files (wind and waves)
https://www.pivotel.com/pivotel-free-weather-grib-files