Forecasters read maps full of symbols to tell what's coming. Today you'll learn the symbols — then you will predict the weather before each map plays out.
Before we start — you've seen weather maps on TV covered in symbols — what do you think those lines and shapes are telling us?
An air mass is a giant body of air that is all about the same temperature. Cold air masses slide down from the poles; warm ones drift up from the tropics.
On the map, the triangles and half-circles always point the way the front is moving. A front is where the weather changes.
Under a High, air sinks — it dries out and skies stay clear. Under a Low, air rises, cools, and forms clouds and rain.