Plain English Meaning

Shapes drawn on a forecast weather chart to show the areas where rain, snow, or other precipitation is expected, with small symbols inside telling you what kind it is.

Full Definition

Outlined areas drawn on a Significant Weather Prognostic Chart that enclose regions where precipitation is forecast to occur. The shape of each polygon shows where precipitation is expected, and symbols inside indicate the type (rain, snow, showers, thunderstorms) and whether it is continuous or intermittent.

Context Anchor

Seen when reading significant weather prognostic charts during preflight weather planning.

Derivation

A polygon is simply a closed shape with straight or curved sides. On these charts, forecasters draw a line around the area where precipitation is expected — that enclosed shape is the polygon.