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fronts 
Contact surface between two air masses with different temperatures and pressure.
surface cold front
Front consisting of a cold air mass that touches the ground and displaces a warm air mass.
upper warm front
Front consisting of a warm air mass that does not touch the ground and slides over a colder air mass.
surface warm front
Front consisting of a warm air mass that touches the ground and displaces a cold air mass.
stationary front
Front that moves very slowly owing to the parallel movement of hot and cold air masses.
occluded front
A composite front that forms when a cold front overtakes a warm front, which it pushes to a higher altitude before joining another cold front.
upper cold front
Front of a cold air mass that does not touch the Earth’s surface and slides over a colder air mass.
