Marine Thunderstorm Wind · Lake Superior

Multiple large spruce and poplar trees were blown down.

A cluster of thunderstorms developed over eastern North Dakota and northwestern Minnesota the evening of Wednesday July 20th. The outflow from the storms coalesced into a couple main bow echoes that quickly sped across northeast and central Minnesota and then over western Lake Superior during the early morning hours of Thursday July 21st. It produced widespread straight-line wind gusts of 60 to 80 mph across northeast Minnesota, especially closer to the Duluth area by the time it reached Lake Superior. One of the hardest hit areas was Duluth, with a couple wind gust reports around 100 mph, including from the Algoma Guardian, a ship that was moving through the Duluth ship canal when the winds struck. The derecho raced across Lake Superior, doing damage to parts of the south side of the Lake along northwest Wisconsin, including to the Apostle Islands.