Hail in Dunn County, North Dakota

A slow moving supercell resulted in an extended period of very large hail and damaging wind gusts in and around the city of Killdeer. Hail up to 3.25 inches in diameter completely covered the ground in many locations. The hail combined with wind gusts of 75 mph to cause extreme damage to buildings, trees, and vehicles in the city. At the Killdeer nursing home windows were broken out and four rooms were damaged to the point where they were not habitable. Two residents sustained minor injuries. The first was injured (direct injury) when they were struck by broken flying glass. The other person was injured (direct injury) as they were evacuating their living area due to broken windows and fell on a wet floor as rain and hail were pouring in. Every field light at the new football stadium was destroyed, and every bus at the school was significantly damaged. Significant damage occurred to vehicles including those at a dealership.

Intense supercells formed in southwest North Dakota during the late afternoon with strong instability and deep layer shear in place. Initial supercells were discrete and very damaging with wind driven 3.25 inch diameter hail falling for an extended period of time in Killdeer, and baseball sized hail falling near Amidon. Damage estimates from the Killdeer area were around $20 million. Upscale growth then occurred with storms forming into a quasi-linear convective system that pushed through central North Dakota and then the James River Valley. Strong thunderstorm winds accompanied the line of storms. Additional elevated storms then formed later in the night over southwest and south central North Dakota as a low level jet increased and an upper level trough approached, with storms continuing overnight.