Derecho tears across South Dakota, southern Minnesota, and Iowa Tuesday

Our latest derecho tore across the Upper Midwest Tuesday afternoon and evening.

The storms formed in South Dakota and morphed into a fast-moving radar signature called a bow echo.

The system produced numerous damaging wind gusts along its path between 70 and 85 mph. Here are a few select wind gust reports.

• 4 ESE Forestburg [Sanborn Co, SD] MESONET reports TSTM WND GST of M81 MPH at 2:38 PM CDT -- MESONET STATION 6 SD RWIS FORESTBURG.

• 3 E Spencer [Mccook Co, SD] EMERGENCY MNGR reports TSTM WND GST of E80 MPH at 3:00 PM CDT -- STOP SIGN BLOWN OVER. ALSO NOTED PEA TO QUARTER SIZE HAIL.

• Springfield [Bon Homme Co, SD] MESONET reports TSTM WND GST of M77 MPH at 3:22 PM CDT -- PERSONAL WEATHER STATION: KSDSPRING9.

• Wall Lake [Minnehaha Co, SD] NWS EMPLOYEE reports TSTM WND GST of E85 MPH at 3:53 PM CDT -- AN NWS EMPLOYEE REPORTED 85-90 MPH WINDS NEAR THE WALL LAKE AREA.

• 3 NNW Sioux Falls [Minnehaha Co, SD] ASOS reports TSTM WND GST of M80 MPH at 4:33 PM CDT -- ASOS STATION KFSD SIOUX FALLS AIRPORT.

• 1 WSW Beaver Creek [Rock Co, MN] MESONET reports TSTM WND GST of M73 MPH at 4:42 PM CDT -- MN006: BEAVER CREEK I-90 MP 4.

Derecho

NOAA’s Storm Prediction Center is calling the large convective storm system a derecho-MCS structure storm.

Derechos are defined as severe convective storms that produce a swath of winds greater than 58 mph along a path at least 240 miles in length.

Here’s more on Derechos from NOAA.

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.

The derecho will continue to move southeast across Iowa and northern Illinois overnight. As of this post, severe thunderstorm watches extend all the way into the greater Chicago area.