What kind of weather system encourages thunderstorms to develop?

Low pressure weather systems. Warm wet air begins rising into the air.  The higher it rises, the cooler it becomes. Water  vapor in the air forms drops. This process is called condensation. The drops join together to form rain, sleet snow or hail.

For a thunderstorm to form, the air has to be full of moisture. Next,  there must be an approaching cold front. Finally the warm air that rises must be warm enough to stay warmer than the air that it passes through.

when these three conditions are met, clouds form and a storm begins.

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