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Lifting Along Fronts
when air masses interact

Lifting also occurs along frontal boundaries as air masses of different temperature and moisture content interact with eachother. For example, as the cold front advances (animation below), it lifts the warm moist air ahead of it. The rising air cools and the water vapor condenses out to form clouds, typically ahead of and along the cold front. Vigorous lifting often occurs along a cold front, resulting in more vertically developed clouds like cumulonimbus clouds.

[Image: diagram of precip development along a cold front (27K)]

In contrast, lifting along a warm front different than what takes place along a cold front. As the warm front nudges against the colder, denser air mass ahead of it, warmer air behind the surface front is forced to ride up and over the frontal surface and over the colder air ahead of it. The lifted air cools and the water vapor condenses out to form clouds in advance of the surface warm front.

[Image: diagram of precip development along a warm front (23K)]

The lifting along a warm front is more gentle when compared with the lifting along a cold front. Consequently, warm frontal clouds are more widespread and less vertically developed. These clouds are occasionally observed up to a thousand kilometers in advance of an approaching warm front.

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Credits and Acknowledgments for WW2010.
Department of Atmospheric Sciences (DAS) at
the University of Illinois at Urbana-Champaign.