Learning Objectives

• Define what air masses are and how weather fronts are formed.

• Classify air masses based on their temperature and moisture characteristics.

• Describe the four main types of fronts: cold, warm, stationary, and occluded.

• Explain the weather patterns associated with each type of front.

Key Vocabulary

Air Mass

A huge body of air that has similar temperature, humidity, and air pressure throughout its extent.

Front

The boundary where two different air masses meet, which often results in weather changes.

Continental

Describes a dry air mass that forms over a large land area, carrying little moisture.

Maritime

Describes a moist air mass that forms over a large body of water, carrying significant moisture.

Tropical

Describes a warm air mass that forms in low-latitude regions near the equator, bringing warm air.

Polar

Describes a cold air mass that forms in high-latitude regions near the poles, bringing cool air.

What is an Air Mass?

• An air mass is a large body of air with uniform properties.

• ​It has similar temperature, humidity, and air pressure at any given height.

• Its characteristics are determined by the area where it forms, its source region.

• Its movement and interaction cause day-to-day changes in weather patterns.

Classifying Air Masses

• Air masses are classified by their moisture and temperature.

• Continental (c) air masses are dry; maritime (m) masses are moist.

• Tropical (T) air masses are warm, forming near the equator.

• Polar (P), Arctic (A), and Antarctic (AA) air masses are cold.

Air Masses of North America

• Air masses are classified by their temperature and moisture.

• Maritime means moist, forming over water; Continental means dry, forming over land.

• Polar air is cold, while Tropical air is warm.

Types of Weather Fronts

Cold Front

• A fast-moving cold air mass pushes a warmer air mass up abruptly.

• This can cause thunderstorms, heavy rain, or snow over a short period.

• Cooler and drier weather follows after the front passes through the area.

Warm Front

• A warm air mass gently slides up and over a colder air mass.

• This movement produces steady, light rain or snow that can last for days.

• The weather becomes warmer and more humid after the front moves through.

Common Misconceptions

Summary

• Air masses have uniform temperature and humidity, classified by moisture and temperature.

• A front is a boundary where different air masses meet, causing weather changes.

• Cold fronts cause abrupt storms, while warm fronts bring steadier precipitation.

• Stationary fronts can result in prolonged wet weather; occluded fronts cause precipitation.