Never mind the strong upfront ad sales for broadcast and cable networks. The slowing economy is “finally starting to impact marketers’ budgets,” UBS Investment Research analyst John Janedis said in a report today as he downgraded his investment recommendations for Discovery Communications and Time Warner and lowered his stock-price targets for Scripps Networks and Viacom. He says the cheering from upfront sales will be short-lived: Broadcasters sold $9.3 billion in inventory, up about 6% from last year, while he expects cable networks to record about $9.2 billion in orders, up about 15% from last year. But advertisers will cancel a lot of those orders later this year. The scatter market “has finally started to slow, which could impact results as early as” the third quarter, he says. Janedis also is concerned about the declining ratings at broadcast networks and says that “cable is also at risk of losing a portion of its audience to other platforms” including online services such as Netflix. The fears about slowing ad sales led him to change his view of Discovery and Time Warner to “neutral” from “buy.” Time Warner has an additional problem in film. With the soft start to Green Lantern, “the success of (Time Warner’s) superhero strategy in a post-Harry Potter world is not a foregone conclusion,” Janedis says.