Outflow

In meteorology, outflow is air that flows outward from a storm system, associated with ridging or anticyclonic flow. In the lower troposphere it radiates from thunderstorms as a wedge of rain-cooled air, visible as a thin rope-like cloud on satellite imagery or a fine line on radar, and for observers on the ground a thunderstorm outflow boundary often approaches in otherwise clear skies as a low, thick cloud bringing a gust front. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/