I'm in Wisconsin now and am checking the weather forecast in advance of the Carolina at Green Bay game. The forecast right now is calling for 1-3 inches of snow in Green Bay Sunday, so it's quite likely it will be snowing on Lambeau Field at some point during this game.
Will this affect the game? Absolutely. But sometimes it's hard to know which way it will go. You'd think snow would always mean a 10-6 defensive battle, but I've seen games where it goes totally the other way. If the receivers can get some traction, they know where they're going and the cornerbacks back-pedaling do not -- sometimes that leads to some quick TDs in "weather" games.
Panthers equipment man Jackie Miles is a true pro and knows all the tricks. He's had the Panthers put baby powder in their cleats before for cold-weather games, and of course he's got all the cold-weather paraphernalia you can imagine to pass out before the game.
The Packers are obviously more used to playing in snow than Carolina, so I would think a real heavy snowstorm would definitely help Green Bay. It's going to be cold, for sure, no matter how much it snows -- the game-time temperature will likely be in the 30s, with winds of 10-15 mph.