It depends on which air mass replaces which in the area. If a cold air mass advances and pushes a warm air mass away, the result is a cold front. When a cold air mass retreats and is replaced by a warm air mass, the result is a warm front. When the two air masses meet and neither advances, the result is a stationary front.
STatioNary Front :):
occluded
occluded
occluded
STatioNary Front :):
It is called a lower pressure front.
A warm front and a cold front must be brought together to form a blizzard
occluded
A stationary front.
Hurricane Sandy interacted with a cold front.
Tornadoes most often form along a cold front.
Stationary