The National Weather Service (NWS) has confirmed that two derechos ripped through parts of South Dakota, Minnesota, Wisconsin, Iowa and Michigan on Friday.
The first derecho, which was involved with Friday's severe weather outbreak, began in east-central Minnesota, producing damaging winds and baseball-sized hail before racing southeast through Wisconsin, across Lake Michigan and eventually dying out 490 miles later in Michigan.
A second derecho erupted in central South Dakota late Friday night and blew through southern Minnesota and into Wisconsin and Michigan. The line of nasty storms lasted an incredible 860 miles.
What the heck is a derecho? It's essentially a long-lived line of destructive severe storms. Here's the official description from the NWS:
"A derecho (pronounced similar to "deh-REY-cho") is a widespread, long-lived wind storm that is associated with a band of rapidly moving showers or thunderstorms. Although a derecho can produce destruction similar to the strength of tornadoes, the damage typically is directed in one direction along a relatively straight swath. As a result, the term "straight-line wind damage" sometimes is used to describe derecho damage. By definition, if the wind damage swath extends more than 240 miles (about 400 kilometers) and includes wind gusts of at least 58 mph (93 km/h) or greater along most of its length, then the event may be classified as a derecho."
Here's an awesome view of the satellite imagery of the first derecho.
The Friday night derecho also produced a couple of confirmed tornadoes in Polk and Barron counties in western Wisconsin.
The first tornado touched down about three miles northwest of Turtle Lake, with the second twister dropping three miles east/northeast of Turtle Lake.
Storm damage assessments revealed that the severe straight-line winds reached a maximum of around 90 mph, with a weather station in Polk County (Cushing, Wisconsin) recording a sustained 73 mph wind for five consecutive minutes.
Further east into Wisconsin, the storm became even more powerful. Here's the description from the NWS in Green Bay.
"Many tens of thousands of trees were snapped or uprooted, resulting in damage to dozens of homes and cottages. The path of the most extreme damage may have been 15 miles wide, and more than 25 miles long. Winds were probably over 100 mph in this area."
The radar replay is impressive, and somehow, the bulk of both derechos almost went around the immediate Twin Cities metro area, although heavy rain and a few reports of trees down from high winds were reported on Saturday.