What type of weather front occurs when a cold air mass replaces warm air?

A cold front occurs when a relatively cold air mass overtakes and displaces a warmer one. Cold fronts are formed when shifting wind patterns cause colder air masses to shift and move into warmer areas.

Because cold air has more density than warmer air, the leading edge of a cold front can create significant atmospheric instability. This occurs when colder air wedges beneath the warmer air contained within another air mass, lifting it upwards. This upwards motion serves to lower atmospheric pressure and often leads to the formation of thunderstorms and showers. Cold fronts are typically stronger during the fall and spring transitions, and weakest during the summer months.