An air mass is a batch of air that has different temperatures and humidity levels throughout it.
Air masses are pushed along by high level winds.
Two air masses meet at a front
At a stationary front air masses move along a landscape.
When a cold air mass takes the spot of a warm air mass it is called a cold front.
A squall line is a line of good weather that forms along a cold front.
A warm front is found where warm air mass slides over a cold air mass.
An occluded front or occlusion usually forms around a high pressure system.
A cloud is the result of a tornado.
Tornadoes form a lot in Illinois.