What type of precipitation is most likely to occur when a warm air mass rises over a cold air mass?

When a warm air mass rises over a cold air mass, the phenomenon often leads to the formation of rain. This occurs due to the process of condensation. As the warm air rises, it expands and cools. Cool air can hold less moisture than warm air, which causes the water vapor in the rising warm air to condense into tiny water droplets. When these droplets cluster together and grow larger, they eventually fall to the ground as precipitation in the form of rain.

In contrast, other types of precipitation like snow or freezing rain typically require specific temperature conditions. Snow is more likely when the atmospheric temperatures are low enough to allow the water vapor to crystallize directly into ice. Freezing rain occurs when rain drops freeze upon contact with very cold surfaces, which generally requires a layer of warm air sandwiched between cold air masses, creating a different scenario than what is described. Hail formation typically occurs in severe thunderstorms where strong updrafts lead to the repeated cycling of water droplets within the storm, growing larger before they ultimately fall.

Thus, under the conditions of warm air rising over cold air, rain is the most likely outcome given the cloud formation and condensation process involved.