NEW YORK (Reuters) - NBC is expected to wrap up its fall season as the No. 1 broadcast network in the key 18-49 advertising demographic for the first time in a decade.
The network's catapult to first place from fourth in the ratings is the biggest surprise so far of the young TV season. The question is how long can its ratings momentum last.
The Comcast-owned network has seen a surge in the fall fueled by two shows that won't be around by the end of December, its red-hot Sunday Night NFL telecast and the hugely popular singing competition "The Voice."
The numbers are shining a positive light on Entertainment Chief Bob Greenblatt, in his second year since moving over from the Showtime cable network. In the first quarter of 2013, however, analysts and advertising buyers say holes in NBC's lineup can't make up for the loss of its two top shows.
"I'm skeptical about whether their ratings are sustainable," said Brad Adgate, who heads research for the advertising firm Horizon Media. "Once those shows go on hiatus or they are doing repeats, I'd be surprised if what they replace with them with will deliver those type of numbers."
When the TV season started, NBC boosted its ratings by adding a second season of the "The Voice" in the fall, instead of airing it only during the spring, and showing it on Mondays and Tuesdays.
The show gave NBC ratings victories in the 18-49 demographic, the age group that advertisers seek, has consistently won its time slots while boosting shows like "Revolution" and "Go On" that followed it.
Total viewers increased from a year ago by 20 percent, to an average of 8.8 million per night, while rivals CBS, FOX and ABC are all down in total viewers.
NBC's ratings engines throttle back without "The Voice," which goes off the air from Dec 17 until March 25. When it returns, it also faces an uncertain reception as new judges Shakira and Usher replace Christina Aguilera and Cee Lo Green.
On December 30, NBC will air its final Sunday night football game of the year, taking prime time's top-rated show with it, Jeff Bader, NBC's president of program planning, strategy and research, said in an interview on Thursday.
NBC's ratings will weaken in January, he conceded. The January-to-March period won't be "necessarily about winning" in the ratings but about getting one or two shows to stick with viewers, he said.
"I wish we had Sunday night football all year, but hopefully these other returning shows will keep us in the hunt," Bader said.
UBS analyst John Janedis predicts that CBS and FOX will move past the Peacock network by the end of the TV season, and CBS' Chief Executive Les Moonves vowed on a November 7 earnings call that his network will finish "on top" and "strong in every single one of the key demos."
"The Voice" served as a launch pad for the hit drama "Revolution," a post-apocalyptic thriller that airs on Mondays and is set 15 years after all the world's electricity stopped functioning. But that show, like "The Voice," is going on hiatus from November 26 to March 25.
Greenblatt has "to make sure that 'Revolution' stays strong, said Optimedia media buyer Maureen Bosetti. "I'm a little bit cautious to say he's a huge success until he's got more solid hits under his belt that he's developed."
NBC will air the weight-loss reality show "The Biggest Loser" in the place of "the Voice" on Mondays, followed by "Deception," a one-hour soap opera about a murder in a wealthy family that replaces "Revolution." On Tuesdays, a reality show called "Betty White's Off Their Rockers" featuring senior citizens playing pranks will take "the Voice" slot.
Ad agency GroupM media buyer Shari Cohen is more optimistic about NBC's chances without "The Voice" and said she is impressed by the network's comeback this season.
"The void will be felt, but there's confidence enough in their strategy and other nights of the week where they have been gaining traction and things that will be coming back in 2013 like 'Smash'," Cohen said.
"Smash," a lavishly produced and heavily promoted musical drama about a Broadway show starring Katharine McPhee and Debra Messing, finished as NBC's top drama in its first season in 18-49 age group and will return for its second season February 5.
The show is heavily championed by Greenblatt, the programming chief who came to Comcast in 2011 after it took control of NBC in a $30 billion deal. When he left the CBS-owned Showtime cable channel, it was in the midst of a phenomenal run of developing hit shows such as "Dexter," "Weeds," and "The L Word" for cable's Showtime network.
Greenblatt's programming performance has been mixed at NBC. He inherited the "The Voice," and had the benefit of this summer's NBC Olympic telecast, which enabled him to promote the fall lineup before the more than 30 million people who tuned into the London games each night.
That gave a boost to "Revolution, "Go On" and "The New Normal," a sitcom from "Glee" creator Ryan Murphy, which were all ordered for full-seasons and are all highly rated new shows. But "Animal Practice," another program that aired in a special preview after one Olympics telecast, was canceled after six episodes.
NBC is coming off a strong third quarter in which its revenue jumped 31.2 percent to $6.8 billion thanks Deto the London Olympics. Excluding the Olympics, its revenue increased 8.3 percent, the company said.
Amy Yong, a sell-side analyst for Macquarie bank, raised her estimates on Comcast in October, citing ratings growth at NBC as a contributing factors.
The NBC model for continued success resembles a strategy employed by Fox, which scheduled shows like "House" and "Bones" after the then-towering ratings champ "American Idol."
Bader, the NBC scheduling executive, said his network will continue to use "The Voice"'s momentum as best it can even as it heads toward its three-month break. After the December 17 finale, NBC will air a preview of a new comedy set in the White House called "1600 Penn."
(Reporting By Liana B. Baker; Editing by Ronald Grover and Leslie Gevirtz)