Fronts

Fronts are zones of transition between two different air masses. The zone may be 20 miles across or it may be 100 miles across, but from one side of a front to the other, one clearly would sense that the properties of an air mass had changed significantly. The frontal zone represents the leading edge of a wedge of cold/cool air. If the wedge is moving into an area of warmer air, the front is called a cold front. If the wedge is retreating and warmer air is moving into an area previously occupied by cool air, the front is termed a warm front.