The NAM (North American) model was upgraded this morning. There are many new updates to the model (see the NCEP TIN link for details), one of the important changes is with the NAM CONUS NEST. It was upgraded from the 4km to 3km horizontal resolution along with a number of physics changes.
The NAM 3Km NEST has been available at Wright Weather for a couple of months running in parallel while NCEP evaluated its output.
Here are the links to the NAM model.
NAM 12KM Model
NAM 3km CONUS Nest
NAM 3km CONUS Nest (Classic) /w upper air products.
Available at 18Z today.
Here is the NCEP TIN outlining some of the changes to the model.