What phenomenon often occurs ahead of a warm front?

The phenomenon that occurs ahead of a warm front is characterized by cloud formation and steady precipitation. As a warm front approaches, warmer air gradually rises over the cooler air at the surface. This lifting of warm air causes it to cool and condense, resulting in the development of clouds, usually starting with high cirrus clouds and eventually leading to thicker stratiform clouds. This process often leads to prolonged and steady precipitation rather than brief and intense thunderstorms.

The gradual ascent associated with warm fronts typically results in lighter and more continuous rainfall, distinguishing it from a cold front, which can produce sudden and severe storms. Therefore, the combination of rising warm air, cloud formation, and steady precipitation aligns directly with the characteristics of what occurs in advance of a warm front.