Strong storms that brought hurricane-force winds to an area stretching from the Upper Plains to the Midwest have been preliminarily classified by the National Weather Service as a derecho, defined as a long-lived line of storms with extreme winds. The weather service's Storm Prediction Center said Tuesday it made the determination based on local storm reports showing straight-line winds gusting well over 60 mph (97 kph) from South Dakota and into Iowa, Minnesota and western areas of Illinois and Wisconsin from late Monday into early Tuesday. A storm is classified as a derecho if its wind damage swath extends more than 240 miles (386 kilometers) and has wind gusts of at least 58 mph (93 kph) or greater along most of the length of the storm’s path.