The area where air masses meet and do not mix. There are four types of fronts.
1)Cold Front:Dense, cold air moves rapidly and runs into a slowly moving warm air mass. The cold air slides under the warm air, pushing it up. Clouds form heavy rain or snow may fall.
2)Warm Front:A moving warm air mass collides with slowly moving cold air mass. The less dense warm air moves over the cold air. Scattered clouds, slowers and light rain fall, lasting for several days.
3)Stationary Front:Cold and warm air masses meet, but neither one has enough force to move the other. Water vapor in the warm air condenses into rain, snow, fog, or clouds. It may stall over an area for several days.
4)Occluded Front:A warm air mass is caught between to cooler air masses. The dense cooler air masses move underneath the less dense warm air mass and push it upward. The warm air mass is cut off. The weather may turn cloudy and rainy or snow.