warm front

A front that results from a mass of warm air sliding over a mass of cold air. On weather maps it corresponds to the line of intersection between the warm frontal surface (WFS) and the Earth's surface. The aforementioned WFS is the zone of separation between a mass of cold air (leading) and a mass of warm air (trailing). Graphically, it is represented by a thick red line with red semicircles set into it, oriented in the direction the front is moving. Stratiform clouds, of great horizontal extent, predominate at warm fronts. The precipitation associated with them is of variable and intermittent intensity, occurring ahead of the position where they are plotted on the maps. In a frontal system, it is positioned ahead of the cold front.