How and why does weather change when a mass of dry cold air meets a mass of warm humid air?

They push against each other along a line called a front. When a warm air mass meets a cold air mass, the warm air rises since it is lighter. … As it rises, the warm air cools rapidly. This configuration, called a cold front, gives rise to cumulonimbus clouds, often associated with heavy precipitation and storms.

How does atmospheric pressure affect weather?

Atmospheric pressure is an indicator of weather. When a low-pressure system moves into an area, it usually leads to cloudiness, wind, and precipitation. High-pressure systems usually lead to fair, calm weather.