Two noted guitarists — Junior Brown and Fabulous Thunderbirds founder Jimmie Vaughan — have signed on for Bob Dylan’s third annual tour of minor league baseball parks. Billed as the Bob Dylan Show, the outdoor concerts have attracted almost 500,000 fans during the past two years. Also appearing on the tour is Texas roadhouse singer Lou Ann Barton. Elana James, formerly of the Hot Club of Cowtown, will open the shows with her new band, the Continental Two. The tour opens Aug. 12 in Comstock Park, Mich., and will hit cities in Ohio, Kentucky, Georgia, North Carolina, Maryland, Pennsylvania, Rhode Island, Massachusetts and New York before ending Sept. 5 in Fort Wayne, Ind.