Air moves into a Low pressure system. It pushes any air that was there upwards.
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Clouds Formed by Air Being Forced to Rise

Some clouds form when air at the Earth's surface is forced to rise. There are three processes that force air to rise.

First, in a low pressure system, wind moves in towards the center from all directions because air moves from high to low pressure. When this air meets in the center, there is nowhere for the air to go but up. Air is also forced to rise when it is traveling over land that slopes upward. The air cools as it rises, and eventually clouds will form. Finally, weather fronts produce clouds by causing air to rise when the lighter warm air flows over the heavier cold air.

All of the cloud types are formed by these processes, especially altocumulus, altostratus, cirrocumulus, stratocumulus, or stratus clouds.

Last modified May 21, 2009 by Becca Hatheway.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA