Plain English Meaning
A weather map that shows what the weather is doing at ground level across a large region — where the highs, lows, and fronts are, and how the pressure is shaped across the area.
Full Definition
A weather chart issued every three hours that depicts the position of pressure systems, fronts, and isobars at the Earth's surface across a wide geographic area. It shows high and low pressure centers, the type and location of frontal boundaries, station weather observations, and lines of equal barometric pressure (isobars), giving pilots a broad picture of the surface weather pattern at a valid time.