The 90th Annual National Christmas Tree Lighting Ceremony is set to take place in Washington, D.C. tomorrow (December 6) beginning at 4:30pm EST.  Award-winning actor Neil Patrick Harris will serve as the master of ceremonies while Kenneth 'Babyface' Edmonds, Colbie Caillat, James Taylor, Jason Mraz, Ledesi, The Fray and Phillip Phillips will perform a collection of holiday favorites during the show.  The 2012 National Christmas Tree Lighting takes place on the Ellipse at President's Park.  The events can be viewed online, live at www.thenationaltree.org beginning at 4:30pm on Thursday.  The ceremony will be broadcast on public television throughout the month of December.