Olympic gold medalist Michael Phelps will be officially welcomed back to his hometown of Towson with a parade Oct. 4, a source close to the event's planning said yesterday. A second celebration will likely take place the same day in Baltimore. Details of the day's festivities in honor of Phelps and other Maryland Olympians are to be revealed today during a noon news conference attended by Gov. Martin O'Malley, Baltimore Mayor Sheila Dixon and James T. Smith Jr., Baltimore County's chief executive. A media advisory issued yesterday by the county's communications office made a point of mentioning that Phelps will not be attending today's news conference at Towson High School, although his mother, Debbie Phelps, is scheduled to be there. The record-shattering 24-year-old swimmer grew up in the Towson neighborhood of Rodgers Forge.