Kevin Myatt is The Roanoke Times' weather columnist.

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"Derecho" is an uncommon term used for an infrequent kind of storm system.

A derecho, as defined by the Storm Prediction Center in Norman, Okla., is "a widespread and long-lived windstorm that is associated with a band of rapidly moving showers or thunderstorms."

On Friday, a derecho zoomed from southeast Kansas across southern Missouri and the length of Kentucky, plus parts of surrounding states, killing at least six people and leaving widespread damage from winds up to 120 mph. The derecho appeared on radar as a line of severe storms stretching into an arched shape known as a "bow echo."

According to the Storm Prediction Center, the word "derecho" was applied in 1888 by University of Iowa physicist Gustavus Hinrichs to distinguish a long-lived straight-line windstorm from the rotating windstorm known by another Spanish-origin term, tornado.

Pockets of circulation within the line of storms spun off several tornadoes on Friday. However, it can be hard to distinguish between damage caused by a derecho's straight-line winds and that caused by medium-strength tornadoes.

Friday's derecho came to the Roanoke Valley to die with a short burst of rain and a few streaks of lightning just before 10 p.m. Additional storms developed to the west and south later, prompting several tornado warnings.

Roanoke got off easy on this one. If the system had rolled across the Appalachians in the middle of a warm, sticky afternoon, we could have ended up sawing trees and picking up debris this Monday morning.

Weather Journal appears on Monday, Wednesday and Friday.