Michael Tynes, 54, of Buffalo, pleaded guilty Wednesday to robbing two Jefferson Avenue branches of the M&T Bank last summer. The robberies occurred from the branch at 133 Jefferson last Aug. 7 and the branch at 1300 Jefferson last Sept. 11. He made off with an undetermined amount of cash in both cases. Assistant U.S. Attorney Mary Catherine Baumgarten said Tynes faces a prison term of up to 20 years and a $250,000 fine or both when he is sentenced at 12:30 p.m. Aug. 15. Buffalo police worked with the FBI’s Safe Streets Task Force in arresting Tynes.