They have to have contingencies in case of a serious weather event. And by "serious" I mean, as bowaic states, "life threatening." You think advertisers wouldn't be pissed if the game got moved to Monday or Tuesday night? That's a worst case scenario. They're only doing that if they have no other choice; i.e. NYC declares a State of Emergency. If it's a run of the mill snowstorm, they're playing on Sunday.
Edit - Yeah..... what they said.
Edit - Yeah..... what they said.