Warm Front
At a warm front, a slowly moving warm air mass collides with a slowly moving cold air mass. Because cold air is denser (heavier) than the warm air, the warm air rides up over the cold air. As the warm air rises, it expands and cools. This is a more gradual process than in a cold front and often forms different cloud types.
If the warm air is relatively dry, scattered clouds may form. If the warm air is humid, showers and light intensity precipitation will fall along the front where the warm and cold air meet.
Because warm fronts move more slowly than cold fronts, the weather may be drizzly or foggy for several days