1. Air Masses of North America

2. Air Masses Important Air Masses Effecting Chicago
Continental Polar Canadian: brings cold air in winter time. Alberta Clipper
Maritime Polar Pacific: brings mild winter weather with moisture. Summer cool weather
Maritime Tropical Atlantic: brings warm moist air from Gulf of Mexico in Summer.

3. High Pressure Systems
High Pressure system: Cool dense dry air. Winds rotate clockwise around high pressure system. Average Barometric Pressure is inches or 1013 milibars.

4. Low Pressure Systems
Warm Front the leading edge of a low pressure system.
Cold Front the trailing edge of the low pressure system

5. Weather Data
Air Temperature: The temperature of the Atmosphere measured in degrees of Fahrenheit.
Barometric Pressure: Is the measure of air pressure. A drop in air pressure indicates the an approaching front
Dew Point: The temperature at which the atmosphere becomes saturated. The higher the Dew Point the more moisture is in the air.
Wind Direction/Speed: The speed of the wind and the direction the wind is coming from. A change in wind direction or increase in speed indicates an approaching front.

6. Weather Data chart