The Avett Brothers have been announced as the surprise guest act for Warren Haynes’ 24th Annual Christmas Jam. As previously reported, Sheryl Crow, The String Cheese Incident, Warren Haynes Band, Trombone Shorty & Orleans Avenue, The Blind Boys of Alabama and more will all be playing the event, which takes place on Saturday at the US Cellular Center in Asheville, NC. The sold-out celebration will also be broadcast live on AXS TV beginning at 6:30pm EST tomorrow.