The Global Ensemble Forecast System Version 12 (GEFSv12) is the current operational global model that issues Medium Range Weather/Subseasonal to Seasonal (MRW/S2S) forecasts at the National Weather Service (NWS) National Centers for Environmental Prediction (NCEP). The GEFS v12, which became operational in September 2020 at the NCEP’s Environmental Modeling Center (EMC) is a major upgrade since 2015, that includes an FV3 dynamical core, increased forecast length (35 days), model resolution (25 km) and ensemble size (31) and coupling with waves and aerosol components, and a 30-year reanalysis and reforecast. 

Please see below links for more details on GEFSv12.

EMC’s GEFV12 page
GEFSv12 official evaluation page by EMC's Model Evaluation Group   

The next GEFS upgrade (v13), (also referred to as Unified Forecast System (UFS) Medium Range Weather/Subseasonal to Seasonal (MRW/S2S) application) will be a coupled atmosphere-ocean-sea ice model that is slated for operational implementation in 2024.