The warmer air rises over the colder air. At the surface, the warm air moves more slowly than the cold air, so the warm air at high altitudes arrives a day or more before the warm air at the surface. As the warm air rises over the cold air, the warm air cools, and moisture in it condenses to form clouds. Typically cirrus clouds form the furthest ahead of the surface front, followed by altostratus and then nimbostratus clouds. If it rains, the rain comes a day or more after the cirrus clouds first appear.
Cold fronts occur when cold air moves into a region previously occupied by warm air.
The storms typically pass fairly quickly.