Thank you for your patience. The approved data access location for inference will remain https://noaahrrr.blob.core.windows.net/hrrr as data is made available each day. You may, however, explore and incorporate additional sources of historical HRRR data during model training. The following two archives might be helpful during training, which provide data dating back to 2014:
You might also consider exploring the python package hrrrb, which provides helpful utilities and code examples to download archived HRRR data in GRIB2 format.