How do fronts change with altitude?

Although the lines on a weather chart show the position of the front at the earth's surface, fronts do not simply rise vertically into the atmosphere — their position changes with altitude. This is due to the fact that hot air rises. As the warm air mass moves in on the cold air mass, the warmer air glides easily over the top of the cooler air. This results in the warm front extending further forward the higher up you go. So the warm front passes overhead at altitude before it passes at surface level.

This is in contrast to a cold front where the front passes over at ground level first. Because the colder air pushes under the warmer air mass, this cold front lags behind at higher altitude.

How fronts affect the weather 

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