High and Low Pressure Systems Air pressure affects the weather. Areas of high pressure are usually where weather is calm and sunny. Areas of low pressure can be stormy. Air pressure is indicated on weather maps with a blue "H" at each center of high pressure and a red "L" at each center of low pressure.

Cold fronts are depicted by blue line with triangles pointing in the direction of motion. Cold fronts demarcate the leading edge of a cold air mass displacing a warmer air mass. Phrases like "ahead of the front" and "behind of the front" refer to its motion.

A meteorologist is a physical scientist who observes, studies, or forecasts the weather.

On a weather map, a stationary front is shown as alternating red semicircles and blue triangles. Notice how the blue triangles point in one direction, and the red semicircles point in the opposite direction.