Front (Cold, Warm, Stationary, Occluded)

The boundary between two air masses of different temperature and moisture. A cold front occurs when cold air advances and pushes under warm air, often causing a narrow band of intense weather including thunderstorms. A warm front occurs when warm air overrides retreating cold air, producing widespread clouds and steady precipitation. A stationary front stalls in place with weather on both sides, and an occluded front forms when a faster cold front overtakes a warm front, lifting the warm air entirely off the surface.