Front

Weather system that causes changes in temperature, cloud cover, precipitation, wind and barometric pressure.

A boundary or transition zone between two air masses of different density, and thus (usually) of different temperature. A moving front is named according to the advancing air mass, e.g., cold front if colder air is advancing.

Front In meteorology, generally, the interface or transition zone between two air masses of different density. Since the temperature distribution is the most important regulator of the atmosphere density, a front almost invariably separates air masses of different temperature. When warmer air replaces the colder, it is a warm front, and a front is a cold one when the opposite occurs.