ENCYCLOPEDIC ENTRY

ENCYCLOPEDIC ENTRY

Front

Front

A front is a weather system that is the boundary separating two different types of air. One type of air is usually denser than the other, with different temperatures and different levels of humidity.

Grades

5 - 8

Subjects

Earth Science, Geography, Physical Geography

















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A front is a weather system that is the boundary separating two different types of air. One type of air is usually denser than the other, with different temperatures and different levels of humidity. This clashing of air types causes weather: rain, snow, cold days, hot days, and windy days.

Two major types of fronts are cold fronts and warm fronts.

Cold fronts often come with thunderstorms or other types of extreme weather. They usually move from west to east. Cold fronts move faster than warm fronts because cold air is denser, meaning there are more molecules of material in cold air than in warm air.

Strong, powerful cold fronts often take over warm air that might be nearly motionless in the atmosphere. Cold, dense air squeezes its way through the warmer, less-dense air, and lifts the warm air. Because air is lifted instead of being pressed down, the movement of a cold front through a warm front is usually called a low-pressure system. Low-pressure systems often cause severe rainfall or thunderstorms.

Warm fronts usually show up on the tail end of precipitation and fog. As they overtake cold air masses, warm fronts move slowly, usually from north to south. Because warm fronts aren't as dense or powerful as cold fronts, they bring more moderate and long-lasting weather patterns. Warm fronts are often associated with high-pressure systems, where warm air is pressed close to the ground. High-pressure systems usually indicate calm, clear weather.

Fast Fact

Fronts on Weather Maps
On weather maps, cold fronts are illustrated by blue lines with sharp "teeth" pointing in the direction of the wind. Warm fronts are illustrated by red lines with rounded bumps pointing in the direction of the wind.

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Writers
Hilary Costa
Erin Sprout
Santani Teng
Melissa McDaniel
Jeff Hunt
Diane Boudreau
Tara Ramroop
Kim Rutledge
Hilary Hall
Illustrators
Mary Crooks, National Geographic Society
Tim Gunther
Editors
Jeannie Evers, Emdash Editing, Emdash Editing
Kara West
Educator Reviewer
Nancy Wynne
Producer
National Geographic Society
other
Last Updated

October 19, 2023

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