1. 1

2. What Makes the Weather Change? 2

3. The kind of weather you are having right now depends on the kind of air mass that is over your area 3 Vocabulary: Air mass A huge body of air that stays together as it moves

4. 4 Air mass has about the same temperature and humidity all through it

5. 1.Cold and dry 2.Cold and wet 3.Warm and dry 4.Warm and wet 5 There are four (4) main kinds of air masses

6. 6 Air masses can form over land or water Those that form over land have dry air

7. 7 Those that form over water have wet air

8. 8 When an air mass forms near the equator, it is warm air

9. 9 When it forms near the poles, it is cold air

10. When two air masses meet, they do not mix 10 Instead, they form a boundary, or front

11. 11 Vocabulary: front A boundary that forms when air masses meet

12. 12 Most changes in the weather take place along fronts

13. The weather changes suddenly when a cold front arrives 13 A cold front forms when a cold air mass moves into a warm air mass

14. 14 Cold fronts may bring partly cloudy skies, rain, or snow Cooler temperatures and clear skies often follow the front

15. 15 Warm fronts may bring wispy clouds, light rain, or snow A warm front forms when a warm air mass moves in over a cold air mass

16. 16 The weather that follows is warm and humid