National Weather Service Weather Forecast Office

Outflow boundaries are storm-scale or mesoscale boundaries separating thunderstorm-cooler air (outflow) from the surrounding air, similar to a cold front, with 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 orgin. New thunderstorms often develop along outflow boundaries, especially near the point of intersection with another boundary such as a cold front or another outflow boundary. Although they can be seen at any time of the year they are more prevalent during the warmer months.

Bobby Boyd
Meteorologist
National Weather Service
Nashville, TN