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Moisture is required for precipitation to develop.
As a parcel of air rises, water vapor will cool and condense, forming tiny water droplets. If there is a lack of moisture, there will not be enough water droplets to form a cloud, let alone precipitation. They are lifting mechanisms, responsible for generating upward motion necessary for precipitation to develop. An air parcel cools as it rises because it expands due to decreasing pressure with height. This expansion causes the air to cool and consequently the water vapor condenses into tiny water droplets.