1. Air Mass Modification

the exchange of heat or moisture with the surface over which an air mass travels.

2. High Pressure System

lower temperatures, clear skies, very small amount of precipitation

3. Low Pressure System

brings wet, warmer temperatures, high cloud cover, high winds

4. Cold Front

when a cold air mass pushes under a warm air mass

5. Warm Front

moving weather front along which a warm air mass slides over a cold air mass, producing stratiform clouds and precipitation

6. Stationary Front

a boundary between air masses that don't move possibly causing rain for several days

7. Occluded Front

a warm air mass is caught between two cooler air masses

8. Hurricane

tropical storm with violent wind and heavy rain

9. Tornado

a powerful funnel-shaped column of spiraling air

10. Smog

mixture of chemicals that occurs as a gray-brown haze in the atmosphere

11. Acid Precipitation

precipitation, such as rain, sleet, or snow, that contains a high concentration of acids, often because of the pollution of the atmosphere