Used when expecting something unpleasant, it prepares the listener for bad news or tough times. With the storm approaching, we're in for some wild weather.
Pro Tip 2/3
Surprising Outcome
Indicates an unexpected result is about to occur, often as a warning or heads-up. He thinks it's a shortcut, but he's in for a long walk.
Pro Tip 3/3
Positive Irony
Sometimes used ironically to suggest that the coming experience might be happily surprising. You're in for a real treat with her homemade cookies.