National Weather Service United States Department of Commerce


Several supercell thunderstorms spawned tornadoes on this day across northeast ND and portions of northwest MN.  These supercell storms produced at least 11 distinct tornadoes, along with numerous large hail and damaging downburst wind events. The largest and strongest of these supercells tracked southeastward for over 110 miles from its origin just west of Larimore ND, past Hillsboro ND and Halstad MN, and continued well east of Detroit Lakes MN, producing 4 of the 11 identified tornadoes, three of which were also the strongest and longest tracking (see descriptions below).

Both a ground survey and an aerial survey were conducted over this long storm track.  These surveys showed evidence of the tornadoes forming and generally tracking southeastward, but occasionally exhibiting a slight curl to the ESE which was followed by a sharp plunge towards the SSE, usually accompanied at this point by an extreme Rear-Flank Downdraft (RFD) wind area, wrapping around to the west and south of the main tornado track.  A good example of this would be Tornado Number 8, which radar imagery and corresponding ground swirl tracks showed as passing well to the northeast of Hillsboro ND, with EF2 tornadic scale winds of from 115-135 mph, while extreme downburst winds of from 80-100 mph raked across the community of Hillsboro itself. 

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