Heavy Rain and Severe Storms, July 15, 2019

radar loop
200-frame radar loop showing evolution of severe thunderstorms over Minnesota on July 15, 2019. Courtesy: College of DuPage.

A hot and humid summer day gave way to intense thunderstorms that affected much of Minnesota on Monday July 15th, with reports of hail, wind damage, and flooding.

Temperatures into the 90s with dew points into the 70s made for the muggiest day of the year to date at many locations. At 3 PM, the air temperature was 91 F at the Minneapolis-St. Paul International Airport, and the dew point temperature was 74 degrees, yielding a Heat Index of 100 degrees F.

The intense heat fueled a stormy episode, which began during the morning, as strong thunderstorms formed in the northwest corner of Minnesota and headed eastward. By late morning, tree damage was reported by foresters around Norris Camp in Lake of the Woods County. The thunderstorms continued eastward, but also started building southward, and by early afternoon, they were scattered from near Fergus Falls to the Canadian border. Hail and power outages were reported in parts of Otter Tail County.

In the late afternoon, as the original storms continued into the Arrowhead region, and towards the Brainerd Lakes area, more thunderstorms developed just west of the Twin Cities,  overspreading the metropolitan area through 8 PM, with reports of hail, flooding, and spotty wind damage. These cells eventually joined forces with the original thunderstorms, and a nearly solid arc of brightly-colored radar echoes marched southeastward through much of the rest of southern Minnesota until late in the night.

The heaviest rains reported extended from Hennepin County on south towards the Waseca area. The largest rainfall amount reported by a MNGage volunteer rain gage  was 5.26 inches at Hamel in Hennepin County;  a nearby CoCoRaHS observer measured 5.16 inches. Totals of 2  to 4 inches were common, much of which fell in 90 minutes. The intense rains flooded roads, small streams, and parking lots, with many cars reported stranded and/or stalled in high waters. At the height of the storm, an estimated 30,000 customers lost power.

 

Updated July 22, 2019