6abc Weather School - What are Fronts?

When you watch weather forecasts on 6abc Action News, you will often hear us talk about weather fronts.

Fronts are contact zones between two different air masses.

A cold front is the leading edge of cooler, drier air. On the weather map, it looks like a blue line with triangles. You can remember that by thinking of the triangles as icicles.

Cold air is more dense than warm air and when it moves in, it wedges under the warm air. That forces the warm air to rise up. When that happens, it cools. Cool air cannot hold as much moisture as warm air so the water in the air is forced out, creating condensation forming clouds, rain and thunderstorms. If there is enough upward lift, those thunderstorms can be severe.

Once the cold front moves through, temperatures drop and the skies clear.

A warm front is the leading edge of warmer air. On a weather map it is a red line with little half circles. You can remember that by thinking of the circles as little suns.

When warm air moves in, it slides over the cooler air, which is more dense. This is called overrunning. It typically creates a steady, light rain that is less intense than the rain caused by cold front storms. Once the warm front moves through, humidity rises and temperatures climb.

If you have any questions or if there are additional topics you'd like me to cover, please click here and fill out the form.
Copyright © 2019 WPVI-TV. All Rights Reserved.