Derecho
A derecho (from Spanish: "derecho" meaning "straight") is a widespread and long-lived, violent convectively induced straight-line windstorm that is associated with a fast-moving band of severe thunderstorms in the form of a squall line usually taking the form of a bow echo. Derechos blow in the direction of movement of their associated storms, similar to a gust front, except that the wind is sustained and generally increases in strength behind the "gust" front. A warm weather phenomenon, derechos occur mostly in summer, especially June and July in the Northern Hemisphere. They can occur at any time of the year and occur as frequently at night as in the daylight hours.
On May 22, 2004, a complex of severe thunderstorms began in the morning around Chicago, IL, moving toward the ESE. The storm complex finally weakened as it approached Washington, DC in the evening hours. Numerous reports were sent to the SPC (see figure below), almost all of them reports of wind damage or measured wind gusts.
Cleveland base reflectivity
Pittsburgh base reflectivity