Tonight, NBC is airing two hours of Grimm. The network is promoting a two hour midseason finale, though technically its running two hour long episodes back-to-back. Last week, Grimm earned a 1.6 adults 18-49 rating, up from a 1.3 on November 29. Will an extra hour of Grimm result in extra big ratings? How do you think the show will fare tonight? While NBC will probably separate the ratings for each episode, since it was billed as a two-hour finale, predict the adults 18-49 rating for the entire two hour block.