This Flash animation relates how precipitation and clouds form along cold and warm fronts. For the cold front, cooler air advances upon warmer air, forcing the less dense warm air upward. Clouds and precipitation form along the front. The warm front is characterized by warm air advancing upon a wedge of denser, cooler air. High level and then increasingly lower level clouds portend the arrival of the warm front. It should be noted that the towering cumulonimbus clouds pictured in this animation usually don't form in the winter due to insufficient temperature contrasts within the atmosphere. The animation can be paused and rewound to stress important points.
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