Plain English Meaning
A long stretch of lower pressure high up in the atmosphere. Air tends to rise within it, which encourages clouds, storms, and bumpy weather.
Full Definition
Elongated regions of lower atmospheric pressure found at altitude rather than at the surface, identified on upper-air charts by southward-dipping contour lines. Troughs aloft are associated with rising air, instability, and unsettled weather, and they often play a role in the development and organization of thunderstorms.
Context Anchor
Seen in weather briefings, weather discussions, and thunderstorm forecasts when explaining why storms may form or grow along a .