A front along which an advancing mass of warm air rises over a mass of cold air.
(meteorol.) The forward edge of an advancing mass of warm air that replaces colder air, usually while causing steady precipitation.
The forward edge of an advancing mass of warm air that rises over and replaces a retreating mass of cooler air. As it rises, the warm air cools and the water vapor in it condenses, usually forming steady rain, sleet, or snow. On a weather map, a warm front is depicted as a red line with half circles whose curved sides point in the direction in which the warm air is moving.