Clouds form in front of a warm front because the warm air mass, which is less dense, slides up gradually over the colder, denser air mass ahead of it. As the warm air rises, it cools at higher altitudes, and the moisture within this air condenses to form clouds. This process creates a broad area of cloud cover, typically sequenced with high cirrus clouds first, followed by progressively lower and thicker clouds such as altostratus and nimbostratus, often leading to precipitation. The gradual lifting of warm, moist air over the cooler air produces extensive cloud formation ahead of the warm front.
