Plain English Meaning

A long line of strong thunderstorms packed close together, stretching across the sky like a wall. The weather along this line is some of the worst a pilot can encounter.

Full Definition

A narrow band of active thunderstorms, often forming ahead of a fast-moving cold front, producing severe weather including strong gusty winds, heavy rain, hail, lightning, and sometimes tornadoes. Squall lines typically extend for tens to hundreds of miles and present a continuous, nearly unbroken wall of storms that cannot be safely flown through or under.

Context Anchor

Seen in weather briefings, radar displays, and preflight weather planning when thunderstorms are organized in a long band.