When a prior passes over an area, it means a change in the weather. Plenty of fronts cause weather events such as rain, thunderstorms, gusty winds, and tornadoes. In ~ a cold front, there might be dramatic thunderstorms. In ~ a heat front, there might be low stratus clouds. Usually, the skies clear when the front has actually passed.

You are watching: Fronts are not included on weather maps because they are unstable.

What is a Weather Front?

A weather front is a shift zone in between two different air masses in ~ the Earth"s surface. Every air mass has distinctive temperature and humidity characteristics. Often there is turbulence at a front, i m sorry is the borderline whereby two different air masses come together. The disturbance can cause clouds and storms.

Instead of bring about clouds and storms, some fronts just reason a change in temperature. However, part storm fronts start Earth"s biggest storms. Dry waves are fronts that build in the tropic Atlantic ocean off the coast of Africa. These fronts can construct into tropic storms or hurricanes if problems allow.

Fronts move across the Earth"s surface ar over many days. The direction of activity is often guided through high winds, such together Jet Streams. Landforms prefer mountains deserve to also adjust the route of a front.

There are four different species of weather fronts: cold fronts, warmth fronts, stationary fronts, and occluded fronts.

Cold Front


A side check out of a cold front (A, top) and also how the is represented on a weather map (B, bottom).

Credit:Lisa Gardiner

A cold front forms when a cold wait mass pushes into a warmer waiting mass. Cold fronts can develop dramatic changes in the weather. They relocate fast, as much as twice as rapid as a warmth front. Together a cold prior moves into an area, the more heavier (more dense) cool wait pushes under the lighter (less dense) warm air, causing it to rise up into the troposphere. Lifted heat air front of the prior produces cumulus or cumulonimbus clouds and also thunderstorms, favor in the picture on the left (A).

As the cold front passes, winds end up being gusty. There is a suddenly drop in temperature, and additionally heavy rain, periodically with hail, thunder, and also lightning. Atmospheric pressure alters from fall to increasing at the front. After ~ a cold front moves with your area, friend may notice that the temperature is cooler, the rain has stopped, and the cumulus clouds are changed by stratus and stratocumulus clouds or clean skies.

On weather maps, a cold prior is represented by a solid blue line v filled-in triangles follow me it, prefer in the map top top the left. The triangles are like arrowheads pointing in the direction the the front is moving. Notification on the map that temperatures in ~ the floor level adjust from heat to cold as you overcome the prior line.

Warm Front


A side see of a warmth front (A, top) and also how that is stood for on a weather map (B, bottom).

Credit: Lisa Gardiner

A warm front develops when a heat air mass pushes right into a cooler air mass, displayed in the picture to the ideal (A). Warm fronts often lug stormy weather as the warmth air mass in ~ the surface ar rises above the cool air mass, do clouds and also storms. Warm fronts move an ext slowly than cold fronts due to the fact that it is more challenging for the warm air to press the cold, thick air throughout the Earth"s surface. Warm fronts often form on the eastern side that low-pressure solution where warmer air from the southern is driven north.

You will often see high clouds favor cirrus, cirrostratus, and also middle clouds prefer altostratus front of a heat front. This clouds type in the heat air that is high over the cool air. As the prior passes over an area, the clouds end up being lower, and also rain is likely. There have the right to be thunderstorms about the warmth front if the waiting is unstable.

On weather maps, the surface place of a warmth front is represented by a heavy red line v red, filled-in semicircles along it, prefer in the map ~ above the best (B). The semicircles show the direction the the prior is moving. They space on the next of the line wherein the former is moving. Notification on the map the temperatures in ~ ground level are cooler in front of the front 보다 behind it.

Stationary Front


A stationary former is stood for on a map by triangle pointing in one direction and also semicircles pointed in the other direction.

Credit:Lisa Gardiner

A stationary front forms when a cold front or warmth front stop moving. This happens once two masses the air are pushing versus each other, but neither is powerful enough to relocate the other. Winds blow parallel come the front rather of perpendicular can help it remain in place.

A stationary front might stay placed for days. If the wind direction changes, the front will certainly start moving again, ending up being either a cold or heat front. Or the front might break apart.

Because a stationary front marks the boundary in between two air masses, there are often differences in wait temperature and also wind top top opposite sides of it. The weather is frequently cloudy along a stationary front, and also rain or snow often falls, specifically if the prior is in an area of low atmospheric pressure.

On a weather map, a stationary former is shown as alternative red semicircles and also blue triangles favor in the photo at the left. Notice how the blue triangles suggest in one direction, and the red semicircles allude in the opposite direction.

Occluded Front


An occluded front is stood for on a weather map through a violet line with alternative triangles and also semicircles.

Credit:Lisa Gardiner

Sometimes a cold front complies with right behind a warmth front. A warm air massive pushes into a colder air fixed (the warm front), and then one more cold waiting mass pushes into the warm air massive (the cold front). Since cold fronts relocate faster, the cold former is likely to overtake the heat front. This is known as an occluded front.

At an occluded front, the cold air mass native the cold former meets the cool air that was front of the heat front. The heat air rises together these wait masses come together. Occluded fronts usually kind around locations of low atmospheric pressure.

There is often precipitation follow me an occluded front native cumulonimbus or nimbostratus clouds. Wind alters direction as the prior passes and the temperature one of two people warms or cools. After the former passes, the skies is usually clearer, and also the waiting is drier.

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On a weather map, displayed to the left, one occluded front looks prefer a purple line with alternating triangles and semicircles pointing in the direction that the prior is moving. It ends at a low push area presented with a huge ‘L’ ~ above the map, begins at the other finish when cold and also warm fronts connect.