Figure 7.4: Warm Front. 3. Based on the diagram of air masses in Figure 7.1, where would you most likely see these fronts developing in the United States? It is important to remember that warm air is typically less dense than cold air. Thus, when they are forced towards each other, in either a warm or a cold front, the cold, usually dry, dense air will remain at the surface and the warm, humid air will rise. That rising humid air cools as it rises, condensation occurs, and clouds form, which may lead to precipitation. The speed and severity of rising will vary based on the presence of a cold front (Figure 7.5) or a warm front (Figure 7.6).