This example is a vacuum though. Last Friday, during the flight for DL1020, there were a bunch of storms in the path for anything coming into LGA from the west...basically a line of storms that would have forced anyone to go south, which is what that flight tried to do. However, if that connecting CR9 was coming in from the South or the Northeast, there were no storms in the way to prevent that flight from getting in. When weather delays flights, it's not just the weather at the arrival or departure fields, but it's often what's in between and what can pass through.