The NAM-NEST is a high resolution 3 Kilometer (“mesoscale”) weather model, last updated in 2017, and is the result of a long evolution of the the very old NGM, the “Eta” model, and the newer NAM (North American Mesoscale Model).
The “NEST” refers to the fact that the horizontal grids are ‘nested’ within the larger 12 KM NAM grid to compute the higher 3km model resolution.
The NAM-NEST is produced every 6 hours at 00z, 06z, 12z and 18z daily.
The NAM-NEST forecasts extend out 60 hours in 1 hour increments.
More complete information can be found here