A surface boundary that is produced by thunderstorm winds.

A boundary separating thunderstorm-cooled air (outflow) from the surrounding air; similar in effect to a cold front, with the passage marked by a wind shift and usually a drop in temperature. Outflow boundaries may persist for 24 hours or more after the thunderstorms that generated them dissipate, and may travel hundreds of miles from their area of origin. New thunderstorms often develop along outflow boundaries, especially near the point of intersection with another boundary (cold front, dry line, another outflow boundary).

storm-scale or mesoscale boundary separating thunderstorm-cooled air (outflow) from the surrounding air

The boundary between an airmass that has been cooled by thunderstorm downdrafts and the unaffected surroundings.

A surface boundary formed by the horizontal spreading of thunderstorm-cooled air. Outflow boundaries may intersect with each other or with other features ( fronts, low-level jets) and act to focus new convection. Outflow boundaries may be short-lived, or last for longer than a day. See gust front.