An air front forms at the confluence
The answer is: Two different air masses.
An air front forms when two different air masses collide.
The two air masses usually have different temperatures, humidity levels, and other characteristics.
When the two air masses meet, they create an unstable layer, the air front.
This layer is characterized by a line of clouds, rain and wind resulting from the temperature differences between the two masses.
Warm fronts are when warm air moves in to replace cold air, while cold fronts occur when cold air replaces warm air.
Fronts can cause extreme weather conditions and it can be dangerous to be around them.
