What causes fog associated with a warm front?

The formation of fog associated with a warm front primarily occurs due to the condensation of moisture. As warm, moist air is lifted over cooler air ahead of the front, it cools and reaches its dew point, leading to the condensation of water vapor into tiny water droplets. This process results in fog because the moisture saturates the air close to the ground, creating the visible mass of water droplets that we perceive as fog.

While evaporation of precipitation can lead to localized fog in certain situations, it is the overall process of condensation that is fundamentally responsible for the widespread fog that forms with warm fronts. The cooling of air as it rises and the consequent condensation of moisture are critical mechanisms that directly contribute to fog formation in this context.