A side view of a warm front (A) and how it is represented on a weather map (B)
Click on image for full size
Windows to the Universe image by Lisa Gardiner
A warm front is where warm air is pushing into colder air. Warm fronts move more slowly than cold fronts. It is harder for the warm air to move against the cold, dense air.
When a warm front passes through, you will often see high clouds like cirrus, cirrostratus, and middle clouds like altostratus before the front passes. These clouds form in the warm air that is high above the cool air. The clouds become lower and rain is likely at the front. There can be thunderstorms around the warm front sometimes too.
On weather maps, a warm front is shown with a solid red line with red, filled-in half circles along it, like in the map on the left (B). The half circles are on the side of the line where the front is moving. Notice on the map that temperatures are cooler in front of the front than behind it.
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