(Mount Vernon, WA)  --  The FBI is now involved in investigating the disappearance of a 14-year-old girl in Skagit County, Washington.  Authorities say Katelynn Barlow vanished Sunday while visiting the Big Lake area from Florida with her family.  Q-13 reports investigators found Katelynn's cell phone at the Smokey Point rest area in Snohomish County near Interstate 5, about 32 miles from where she was last seen.  Authorities describe Katelynn as white, five-foot-one, about 120 pounds, with shoulder-length red hair.  Anyone who sees her is asked to call 911.