Which fog forms in advance of a warm front when warm rain falls into a layer of cold and moist air?

Which fog forms in advance of a warm front when warm rain falls into a layer of cold and moist air?

• A. Evaporation/Steam fog
• B. Frontal fog
• C. Radiation fog
• D. Ice fog

Answer: (B)

Frontal fog forms when warm, rain-bearing air from an advancing warm front moves into a layer of cool, moist air near the surface. As the rain falls into that cooler air, it evaporates and raises the humidity until the air is saturated at the surface. The tiny droplets then condense, creating fog that often sits ahead of the warm front. This distinguishes it from other fogs: radiation fog requires clear skies and overnight cooling, steam fog forms from warm air over a cold water surface, and ice fog occurs in very cold air with ice crystals forming directly from water vapor.

Frontal fog forms when warm, rain-bearing air from an advancing warm front moves into a layer of cool, moist air near the surface. As the rain falls into that cooler air, it evaporates and raises the humidity until the air is saturated at the surface. The tiny droplets then condense, creating fog that often sits ahead of the warm front. This distinguishes it from other fogs: radiation fog requires clear skies and overnight cooling, steam fog forms from warm air over a cold water surface, and ice fog occurs in very cold air with ice crystals forming directly from water vapor.