What will be the effect on the reading of an altimeter of an aircraft parked on the ground, shortly before an active cold front passes over the airport?

When considering the behavior of an altimeter during weather changes, particularly with the approach of a cold front, it's important to understand the effects of atmospheric pressure on altimeter readings. An altimeter functions by measuring atmospheric pressure. As a cold front approaches, it usually brings a decrease in atmospheric pressure at the surface. Therefore, as the pressure drops, the altimeter will register a lower altitude, leading to an increase in the reading.

Given that the altimeter is calibrated to indicate altitude based on local atmospheric pressure, the decreasing pressure due to the incoming cold front will result in an increase in the altimeter reading. Simply put, a cold front typically causes a drop in pressure, leading the altimeter to indicate a higher altitude than the actual one if it's not adjusted accordingly.

Understanding this phenomenon is critical for pilots and those in aviation as it affects flight operations, navigation, and the safety of the aircraft. Keeping an eye on barometric changes helps ensure that altimeter settings are adjusted to maintain accurate altitude readings, particularly when transitioning between different weather conditions.