A cold front is the leading edge of a cooler mass of air at ground level that replaces a warmer mass of air and lies within a pronounced surface trough of low pressure. As a cold front comes in and drives under the mass of warm air, the warmer and moist air will be forced upwards. As the warm air is pushed higher, the moisture it carries condenses and falls as rain. This is why a lot of heavy rain is produced along a cold front but once the cold air mass has come in, this often abruptly changes to a clear spell of weather. Cold fronts typically create tall cumulus and cumulonimbus clouds which can produce thunderstorms. Severe weather is more common during a cold front passage and may include rapid development of heavy rain showers, lightning, hail, and/or tornadoes. Eventually, good visibility prevails once the cold air dominates the area. Temperatures remain cooler, and because cold air is more dense, the barometric pressure continues to rise.