The fronts represent the separation surfaces of two air masses at different temperatures.
Their study and evolution (known as frontogenesis) is essential to determine current weather conditions and their evolution including winds, cloud systems and precipitation.
You have a cold front when a cold air mass meets a hot one.
Being the heaviest cold one wedges under the heat causing it to rise quickly and cool.
This type of front causes very intense precipitation related to vertical development clouds that are generated due to the rapid rise and cooling of the mass of hot air.
The expected cloud system ranges from the Cirri present in the most extreme part of the front at altitudes between 6 to 8 km, high mounds between 4 and 5 km and low clouds such as stratocums and mounds between 1 and 2 km.
These cloud systems, which develop in the hot air zone do not bring precipitation to the geographical area below but are indicators of the advance of the front in the presence of decreasing pressure and temperature.
In the area affected by the precipitation there are large clouds of vertical development, Cumulolembi based below 1000m altitude and hat that reaches up to 6-7km altitude.
In this area the rainfall is very violent and abundant, often of a thunderstorm character.
Other small precipitation is found in the area of interest of cold air and is due to the formation of small mounds.
It can be summarized by saying that:
Before the arrival of the front: stationary temperature, decreasing pressure, wet southwest winds in the Northern Hemisphere, high-bank banks and subsequent pile-nembi massing.
In the area of interest of the front: decreasing temperature, pressure increasing even sharp, wind from west to northwest stormy and cold even in gusts, rain showers often with lightning and thunder.
After the front: Rapid calming, pressure rising more steadily, wind from the northwest less strong and cold, temperature decreasing.
The areas affected by the cold front unlike the warm front are restricted, 300km-400km, while the precipitation area is limited to about 100km.
On weather maps they are indicated by a line with blue triangles.