"warm front." YourDictionary, n.d. Web. 16 January 2019. <https://www.yourdictionary.com/warm-front>.
warm front. (n.d.). Retrieved January 16th, 2019, from https://www.yourdictionary.com/warm-front
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.