Arrow will say goodbye after eight seasons with a two-hour series finale event on Tuesday, Jan. 28 that will kick off with a one-hour retrospective special. Supernatural will wrap up 15 seasons on Monday, May 18. Supernatural will move to Mondays -- the only weeknight that it hasn't aired during its long WB/CW tenure -- starting on March 16. Also on March 16, The CW will launch the second season of Roswell, New Mexico. The CW also announced that Riverdale spinoff Katy Keene will debut on Thursday, Feb. 6.