Final answer:
The polar front jet stream is located at the boundary between warm and cold air masses, influencing weather patterns through its meandering flows.
Step-by-step explanation:
The polar front jet stream can be found at the boundary between warm and cold air. This boundary separates the polar cell from the ferrel cell, and the temperature difference between these masses of air creates the jet stream. The polar front jet stream does not fit the description of the other options because it is not solely found poleward of the Rossby waves, over the North and South poles, near the Earth's surface, or embedded in easterly flow far aloft.