The formation of a front occurs when two adjacent air masses with different densities and temperatures meet and strengthen the discontinuity between the air masses. It occurs most frequently over continental land areas such as over the Eastern US when the air mass moves out over the ocean. It is the opposite of frontolysis.
The birth or creation of a front. This occurs when two adjacent air masses exhibiting different densities and temperatures are brought together by prevailing winds, creating a front. It could happen when either air mass, or both, move over a surface which strengthens their original properties. However, it occurs most often along the eastern coasts of North America and Asia, when the air mass moving out over the ocean has a weak or no distinct boundary. The opposite of frontolysis.