Air moves into a Low pressure system. It pushes any air that was there upwards.
Click on image for full size
Windows to the Universe original image
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.
You might also be interested in:
Wind is moving air. Warm air rises, and cool air comes in to take its place. This movement creates the winds around the globe. Winds move at different speeds and have different names based on their speed....more
Weather fronts can cause clouds to form. Fronts happen when two large masses of air collide into each other at the Earth's surface. Warm fronts produce clouds when warm air replaces cold air by sliding...more
Altocumulus clouds are part of the Middle Cloud group. They are grayish-white with one part of the cloud darker than the other. Altocumulus clouds usually form in groups. Altocumulus clouds are about...more
Altostratus clouds belong to the Middle Cloud group. An altostratus cloud usually covers the whole sky. The cloud looks gray or blue-gray. The sun or moon may shine through an altostratus cloud, but will...more
Cirrocumulus clouds belong to the High Cloud group. They are small rounded puffs that usually appear in long rows. Cirrocumulus are usually white, but sometimes appear gray. Cirrocumulus clouds are the...more
Stratocumulus clouds belong to the Low Cloud group. These clouds are low, lumpy, and gray. These clouds can look like cells under a microscope - sometimes they line up in rows and other times they spread...more
Stratus clouds are part of the Low Cloud group. They are gray and can cover most or all of the sky (like a big blanket). Stratus clouds sometimes produce light mist or drizzle. ...more