Minor flooding with light wind damage near the DNR building at the State Fair, from two waves of storms August 26 and 27th, 2024. Photo courtesy of A. English.
Two waves of severe thunderstorms affected parts of central and southern Minnesota Monday August 26 into Tuesday August 27, knocking down trees and knocking out power, with many areas hit equally hard by both waves.An extremely humid and very warm air mass overspread most of Minnesota on Monday, August 26. Stations across the state registered dew point temperatures in the middle to upper 70s F with some rare low 80s F dew points reported in southern parts of the state.* Combined with temperatures in the 80s to low 90s F, the moisture drove Heat Index values to the 100-110 F range, especially in southern and eastern areas.The heat and humidity created a very unstable air mass, and a series of disturbances along with a cold front, primed the region for explosive thunderstorm development.The first severe thunderstorms of the day developed in Otter Tail County in the early afternoon. As Time wore on, this storm faded, but other larger and more intense ones developed to its south. Eventually, a massive complex of storms reaching up to 12 miles high at times, formed to the west of the Twin Cities, in Renville, Sibley, McLeod, Meeker, and Stearns counties.These storms pushed eastwards, making it to the western Twin Cities metropolitan area by 6:00 PM, and into Wisconsin between 8 and 9 PM. These storms produced gusty winds of up to 65 mph, uprooting trees and leaving behind up to 100,000 power outages, primarily but not only in the Twin Cities area.Meanwhile, a second wave of thunderstorms was developing in western South Dakota, and this pushed east-northeastward at varying intensities throughout the night, but began gaining strength as it passed from southwestern into southern, central, and eastern Minnesota. Winds once again gusted up to 65 mph in parts of the Twin Cities metropolitan area between 5 and 6 AM, including a report of 58 mph at a station 1/2 mile from the State Fair, where the winds damaged some trees and vendor facilities.This new wave of storms produced an additional surge in power outages, with totals reaching almost 150,000 at the height of the storm.The two waves of intense thunderstorm activity also produced pockets of heavy rainfall, with many areas picking up totals of 1 to 2 inches, with reports of 2 to 2.75 inches from National Weather Service and CoCoRaHS observers near Willmar, Glencoe, Chanhassen, Minneapolis, St. Michael, and Cambridge. No major flooding was reported in Minnesota from these storms.
*Some small airport stations appeared to record even higher dew points, in the middle 80s F (as high as 86 F), but these values were likely in error. Some stations routinely report much higher dew point values than other nearby and/or similarly situated stations, and appear to be suffering from sensor error. Aug 27, 2024KAB
