 A cold front is located at the leading edge of the temperature drop off , which in an isotherm analysis shows up as the leading edge of the isotherm gradient , and it normally lies within a sharp surface trough . Cold fronts often bring heavy thunderstorms , rain and hail . Cold front can produce sharper changes in weather and move up to twice as quickly as warm fronts , since cold air is denser than warm air and rapidly replaces the warm air preceding the boundary . On weather maps , the surface position of the cold front is marked with the symbol of a blue line of triangle @-@ shaped pips pointing in the direction of travel , and it is placed at the leading edge of the cooler air mass . Cold fronts come in association with a low @-@ pressure area . The concept of colder , dense air " wedging " under the less dense warmer air is often used to depict how air is lifted along a frontal boundary . The cold air wedging underneath warmer air creates the strongest winds just above the ground surface , a phenomenon often associated with property @-@ damaging wind gusts . This lift would then form a narrow line of showers and thunderstorms if enough moisture were present . However , this concept isn 't an accurate description of the physical processes ; upward motion is not produced because of warm air " ramping up " cold , dense air , rather , <unk> circulation is behind the upward forcing . 
