ABC's much-hyped FlashForward made a big flash in its debut on Thursday as it averaged 12.5 million viewers and beat CBS's usual winner in the 8 00 p.m. timeslot, Survivor , which rounded up 11.9 million viewers for the current permutation shot in Samoa. FlashForward also provided some impressive coattails for ABC to ride with a two-hour edition of Grey's Anatomy , which followed, averaging 16.7 million viewers. It was not a good night for Jay Leno, however. His second Friday managed to attract just 5 million viewers, a figure slightly below his average for the Tonight show.