Which type of front is characterized by warm air moving into an area previously occupied by cooler air?

A warm front is characterized by warm air moving into an area that was previously occupied by cooler air. As this warm air mass advances, it gradually rises over the cooler air mass because warm air is less dense. This leads to a typical sequence of weather changes as the warm air cools at higher altitudes, resulting in cloud formation and often precipitation. Warm fronts generally bring extended periods of light to moderate rain, and the transition from the cooler air mass to the warmer one can lead to a gradual increase in temperatures and shifting wind patterns.

In contrast, cold fronts involve the movement of colder air displacing warmer air, resulting in more severe weather changes, such as thunderstorms. Stationary fronts occur when neither air mass is strong enough to replace the other, leading to prolonged, possibly unsettled weather in the area of the front. Occluded fronts, which form when a cold front overtakes a warm front, can involve interactions that create complex weather patterns but do not primarily focus on the advancement of warm air into cooler areas. Therefore, the defining characteristic of a warm front aligns accurately with the described phenomenon in the question.