Courtesy of Iowa State University, Environmental Mesonet
The most significantly damaging thunderstorms of 2023 (so far) developed over central, eastern, and southern Minnesota on Friday August 11th, producing heavy hail and strong winds, and striking the Twin Cities right as people were leaving work for the weekend.
The storms formed as strong winds aloft overspread an unstable air mass at the surface, ahead of a cold front. The first thunderstorm formed just after noon in northern Otter Tail County, and then intensified as remained west and south of Brainerd through 2:30 PM, producing hail the size of golf balls and walnuts near Pierz in Morrison County. This storm moved east-southeastward, becoming even stronger near Mora, where it produced a 76 mph wind gust at the airport, and where it snapped trees and knocked out power while producing large hail.
As the first storm continued towards the St. Croix River near the Pine and Chisago County border, producing additional hail and wind damage, other storms developed quickly to the north, northwest, and west of the Twin Cities between 3:30 and 4:30 PM. Many of these storms were monstrous, reaching heights of over 50,000 feet, and most of them produced large hail or damaging winds at some point.
One particularly intense storm tracked from south of Willmar to south of Rochester during the early evening, producing a continuous swath of strong winds and half dollar to golf ball-sized hail, with hail the size of baseballs reported north of Buffalo Lake in Renville County.
Four similarly powerful thunderstorm cells moved across the northern, western, central, and eastern portions of the Twin Cities area between 4:30 and 6:30 PM. The large thunderstorms darkened the skies, forcing streetlights on across virtually everything inside the 494/694 loop, as constant thunder and vivid lightning signaled the approach of the storms. Hail the size of ping pong balls, golf balls, tennis balls, and even baseballs pounded the most heavily populated portions of the Twin Cities, leaving streaks of hail damage stretching across Plymouth, Robbinsdale, Golden Valley, St. Louis Park, Edina, Minneapolis, Richfield, and St. Paul. The storms struck the two downtowns as bars, clubs, and restaurants were filling up with Friday crowds, many of whom then witnessed golf ball-sized hail or larger banging off of windows and smashing on the pavement outside. Winds intensified as these storms crossed the Mississippi River, and the St. Paul airport at Holman Field reported a wind gust to 68 mph.
The storms produced extensive damage to vehicles, rooftops, windows, and siding. The extent of damage from these storms may be hard to estimate because so much property is covered by personal insurance policies, but this storm appears to have produced larger hail over a larger population than the intense hail storm of May 19, 2022.
Additional storm cells in southwestern and southern Minnesota produced large hail and wind damage as well.
September 1, 2023