1. Weather Fronts
8th Grade

2. Weather front – The area where two air masses meet and do not mix.
Definition
Weather front – The area where two air masses meet and do not mix.

3. Front and Weather
Different types of fronts produce different patterns of weather.
There are four types of weather fronts:
1. Cold Fronts
2. Warm Fronts
3. Stationary Fronts
4. Occluded Fronts

4. Cold Front
As you know, cold air is dense and tends to sink while warm air is less dense and tends to rise.
When rapidly moving cold air mass runs into a slowly moving warm air mass, the denser cold air slides under the lighter warm air.
The warm air is then pushed upward.
The front that forms is called a cold front.
Cold fronts move quickly.

5. Cold Front

6. Warm Fronts
At a warm front, a moving warm air mass collides with a slowly moving cold air mass.
Because cold air is more dense than warm air, the warm air moves over the cold air.
Warm fronts move more slowly that cold fronts.

7. Warm fronts

8. Stationary Fronts
Sometimes cold and warm air masses meet, but neither one has enough force to move the other.
In this case, the front is called a stationary front.
Where the warm and cool air meet, water vapor in the warm air condenses into rain, snow, or just clouds.
If a stationary front remains stalled over an area, it may bring many days of clouds and precipitaion.

9. Stationary Fronts

10. Occluded Fronts
At an occluded front, a warm air mass is caught between two cooler air masses.
The denser cool air masses move underneath the less dense warm air mass and push it up.
The two cooler air masses meet in the middle and may mix.
The temperature near the ground becomes cooler and the warm mass is cut off.

11. Occluded Fronts

12. Weather Front Symbols
Cold Front: A cold front indicates a colder air mass is moving in the direction toward which the triangles are pointing.
Warm Front: A warm front indicates a warmer air mass is moving in the direction toward which the semicircles are pointing.
Stationary Front: A stationary front separates a warmer from a cooler air mass.
Occluded Front: An occluded front is drawn in purple

13. Vidoe

14. Using the key, can you tell me what’s happening on this map of the United States?

15. Current weather
Use this map to describe what fronts are currently going on in the United States.

16. Fun Facts
Like fingerprints or snowflakes, no two fronts are exactly alike. For example, the slope of a front can vary considerably, from about 1:100 (I km of vertical distance covers 100 km of horizontal distance) for a cold front to about 1:200 for a warm front!
The slope of the front is an important determinant of the type of weather the front brings. A cold front with a very steep slope is likely to bring a narrow band of violent storms extending less than 100 km. A warm front with a very gradual slope is likely to bring cloudy weather but no storms. However, the area affected by the cloudy weather may extend for many hundreds of km!