Flash Flood in Sanilac County, Michigan

Thunderstorms with very heavy rain repeatedly occurred across the same areas and dumped rain at a rate of nearly 2 inches per hour. Doppler radar estimated that 5 inches of rain fell in a west to east swath across southeast Sanilac County, and as much as 10 inches in an isolated area in and around the Brown City area. A cooperative observer in Brown City actually measured 7.35 inches over a 4 hour period on the evening of August 2nd, with an additional eight tenths of an inch falling after midnight during the early morning hours of the 3rd. The most intense rain fell from about 2000 EST on the 2nd to about 0100 EST on the 3rd. Flash flooding began around 2300 EST. Many homes in the Brown City area were heavily damaged by flood waters. The entire town experienced flooding and the city manager reported 220 damage claims filed with the city. At least 3 basements were lost and and a few homes reported nearly $100K in damages. The entire lower half of the high school was flooded with 3 to 5 inches of water. Flood waters reached 3 feet deep in a mobile home park in the city. Around 0200 EST on the 3rd, the flood waters stopped rising, and by noon, the flood waters began to recede. Total property damages were estimated at $1.25M. No injuries were reported.

A cold front moved through the area during the evening of August 2nd and finally brought an end to the five day heat wave that had plagued southeast Michigan. Thunderstorms, a few intense, fired up out ahead of the cold front within the unstable airmass in place across southeast michigan. The severe weather was primarily confined to areas along and just south of the I-69 corridor. This was mainly a wind event with reports of several trees blown down. Most significantly, a tropical-like airmass and repeated rounds of storms along the I-69 corridor caused flash flooding in Lapeer and Sanilac counties, with extensive damages occurring in and around the Brown City area.