Codex · Cloud
Shelf Cloud
A low, wedge-shaped cloud on the leading edge of a storm, formed where cool outflow lifts warm air. It marks a gust front, not a tornado.
How to spot it
A long, horizontal, layered cloud that looks like a shelf with a smooth top and a ragged bottom, often with a bright gap of sky ahead of it.
On radar
A thin line of high reflectivity along the leading edge of a storm line or bow echo.
Safety
A shelf cloud means strong straight-line winds are about to arrive. Get indoors or away from trees and signs.
Related
Last reviewed 2 November 2026