What is the effect on an altimeter reading as a cold front approaches?

When a cold front approaches, the atmospheric pressure generally increases as the front moves in. This happens because cold air is denser and can lead to higher surface pressure. An altimeter, which measures atmospheric pressure to infer altitude, is calibrated to standard atmospheric pressure. When the pressure rises, the altimeter would indicate a higher altitude than actually exists. Therefore, as a cold front approaches and pressure increases, the altimeter reading rises, leading to an increase in the indicated altitude.

This dynamic illustrates the relationship between weather systems and pressure changes. In this case, the rising altimeter reading correctly reflects the changes in atmospheric conditions associated with an approaching cold front.