Cold fronts and Warm fronts
A cold front is a mass of cold air that displaces the warmer stormy weather
can be associated with it. For example, heavy rains can occur because of
a cold front.
Similarly, a warm front is a mass of warm air that displaces the colder air at
the surface. However, a warm front cannot overtake a cold front, because
the air associated with a warm front is lighter in weight, therefore it slides
over or overruns the cold air instead.
Weather associated with a warm front lasts longer than weather that is
associated with a cold front, because air in a warm front rides over a
wedge of cold air. The air cools over the slope of colder air, condensing
into clouds that may develop into rain or fog near the front.
Source: Monkeyshines on Health & Science, Jan2003 Atmosphere, p33,
1p