By Jonelle Fuller
A could front occurs when a fast moving cold air mass runs into a slowly moving warm air mass. Because cold air id denser than warm air, the cold air mass remains close to the ground and sinks under less dense warm air masses. As the warm air moves above the cold, the warm air mass cools. It soon will chill to the temperature at which the water vapor in the air condenses and turns into rain droplets of liquid water.
With a warm front, a slowly moving warm air mass collides with a slowly moving cold air mass. Because cold air is denser than warm air, the warm air mass rises over the cold air. Clouds, storms, and rain often accompany warm fronts. If the warm air is dry, scattered clouds form. If the warm air is humid, showers and light rain fall along the front where the warm air mass meets the cold air mass. Because warm fronts or foggy for several days.
Some times cold and warm air masses meet, but neither one has enough force to move the other. The tow air masses face each other in a stand off. In this case, the front is called a stationary front where warm and cold air masses meet, water vapor in the warm air condenses into rain, snow, fog, or clouds.
The most complicated weather situation occurs at an occluded front. At an occluded front, a warm air mass is caught between two clod fronts and the denser cold air masses both push it upwards the two air masses meet in the middle and could mix.