Storms are the result of conflict between warm air masses and cold air masses. The zone of contact between the contrasting air masses is called a front. Fronts are classified as cold fronts or warm fronts depending on which air mass is dominant. When the cold air mass is dominant, the change occurs quickly because cold air masses usually move rapidly. Cold air is heavier than warm air; therefore, the warm air is forced upward, as shown in the cross section in Figure 16.2.

As it rises, warm air cools rapidly. Extreme turbulence and heavy rainfall may occur over small areas. From a soil and water conservation standpoint, cold fronts may cause local rainstorms of high intensity that may result in serious soil erosion and local flooding.

Cold air

FIGURE 16.2. Cross section of a cold front.

Cold air

A cross-sectional view of a warm front is shown in Figure 16.3. A warm front occurs when the warm air mass is dominant and overtakes cooler air. The rate of cooling is much less than for a cold front, and resulting rains are gentler. The rains usually cover very large areas. Thus the potential for erosion is reduced, but the rains may cause widespread flooding if they persist for a long period of time.

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