VII. Remind participants that their first preference should always be to avoid an adverse weather situation. This module deals with what to do if you havenít been able to avoid it. You will discuss those situations where the school bus driver has to decide what to do.
VII.A. Tell participants that all the information covered in this section will be on a handout which you will distribute shortly.
VII.D.6. The heaviest lake-effect snow episodes usually occur when a bitter cold outbreak dives southeast across the Great Lakes. As cold air flows over the warm water, the bottom layer of air over the surface of the water is heated from below. Moisture also evaporates into the air as it is heated. Since warm air is lighter and less dense than cold air, the heated air rises and begins to cool. As the air cools, the moisture that evaporated into it condenses and forms clouds. When enough moisture condenses out of the air, snow falls over the regions downwind of the Great Lakes. The greater the temperature contrast between the cold air and the warm water, the heavier the snow showers will be. If the temperature contrast is great enough, the rising air will have enough buoyancy to form thundersnow, which are thunderstorms that have snow falling out of them rather than rain.
VII.E. When temperatures are near freezing, falling snow hits the pavement, melts, and then freezes. This creates a layer of ice that is then covered with snow.
VII.F. Distribute Handout #6, Slippery Roads - Snow. Review it with the participants.