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2024 Hennepin County All -Jurisdiction Hazard Mitigation Plan <br />Volume 2 — Hazard Inventory <br />The 1-94 Derecho of 1983 <br />Around dawn on the morning of Tuesday, July 19, 1983, well north of warm/stationary front over <br />South Dakota and northern Iowa, a bow echo moved out of northeast Montana and began <br />producing damaging winds in northwest North Dakota. This would be the beginning of a <br />noteworthy progressive derecho event that would move across the northern Great Plains and <br />upper Mississippi Valley and reach the Chicago metropolitan area by late evening. <br />As the convective system's cold <br />pool continued to deepen and <br />elongate east -southeastward with <br />the mean cloud -layer flow, it <br />ultimately reached the warm front <br />as that boundary advanced slowly <br />north across eastern South Dakota <br />and southern Minnesota. This <br />meeting occurred during the early <br />afternoon over west central <br />Minnesota, and likely accounts for <br />the appreciable increase in storm <br />strength observed around that time <br />as the convection became surface <br />based. At this time the storm <br />system also expanded in scale, evolving into a squall line with two and sometimes three bow echo <br />segments as it continued across Minnesota and later Wisconsin, with Interstate 94 near its central <br />axis. <br />The path of the 1983 1-94 Derecho as it crossed over six states on <br />July 19, 1983. <br />Winds over 100 mph were recorded at the airport in Alexandria, Minnesota, Minnesota, where <br />planes and hangers were damaged and destroyed. The storm continued to produce much damage <br />as it moved east-southeast across south central and southeast Minnesota; approximately 250,000 <br />customers lost electrical power in the Minneapolis/St. Paul area, a record at that time. Thirty-four <br />people were injured in Minnesota and Wisconsin from this storm. Of these injuries, 12 were from <br />mobile homes being blown over, and eight were from falling trees. <br />The Northwoods/ "Right Turn" Derecho of 1995 <br />During the late afternoon of Wednesday, <br />July 12, 1995, thunderstorms formed over <br />southeast Montana and began producing <br />winds that damaged homes and barns. As <br />the storm system moved east across North <br />Dakota, vehicles were overturned, and a <br />grain bin was destroyed. Measured winds <br />reached 70 mph at Bismarck, ND. As the <br />system approached Fargo during the early <br />morning of July 13th, it became a well- <br />defined bow echo storm with measured <br />winds of 91 mph at the Fargo airport. The <br />_ "JULY r <br />03 <br />Mr ND 1AM �.N rm7 <br />lawn <br />C BST CCY '�+ <br />M3 L 4 k <br />W mm,�. cltm r,h <br />C07 11RM nl l'i t_ +Mro <br />O ` SD MN WI TDT ant i '"*,,, }N <br />c0T <br />+' <br />tDT <br />three derechos to occur on consecutive days across <br />Northern Minnesota. <br />87 <br />