Derecho called one of the worst in the past decade

The deadly squall line that raked far southern Illinois midday Friday,
devastating the Carbondale area on its way across a 1,200-mile swath of
terrain covering sections of nine states, is one for the books. Dr. Joe
Schaefer, director of the National Oceanic and Atmospheric Administration's
Storm Prediction Center, says the "derecho complex is one of
the worst I've seen in the past decade."
Derecho is the term applied to a uniquely long lived and damaging
line of thunderstorms. Their straight line winds and occasional
tornadoes can produce damage over hundreds of miles -- at times, even a
1,000 miles or more. Friday's squall line began as scattered thunderstorms
on the Colorado-Wyoming border, then organized into a line
that was still going strong as it reached eastern Tennessee and the
Carolinas. A second line of storms raced across Illinois late Friday --
this one producing 70 m.p.h. gusts south of the Quad Cities and a brief
tornado touchdown near Little York in western Illinois. The storms
sweep into the Chicago-area overnight, ushering much cooler air into
the region for the Mother's Day weekend.
--Tom Skilling, Chief Meteorologist, WGN-TV/Chicago Tribune