Midwest Weekly Highlights - September 24-30, 2009

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Temperature

For the last week of September temperatures averaged fairly close to normal across the Midwest (Figure 1). The coolest temperatures (2-3°F below normal) were in western Missouri and southwestern Iowa. The warmest temperatures were located in northwest Minnesota where they averaged more than 4°F above normal. Early in the week temperatures were warm but that changed following the passage of cold front on September 27th (Figure 2) which brought a shot of cool fall air to the Midwest. Strong northwest winds over the next three days brought an end to the above normal temperatures, even spreading frost and freeze conditions across parts of the upper Midwest (Figure 3). Few temperature records were set during the week.
 

Precipitation

Precipitation totals varied across the Midwest during the week. Percent of normal precipitation varied from < 25% to more than 200% (Figure 4). Wet areas extended from southwest Minnesota to northeast Missouri, from Upper Michigan to west central Lower Michigan, and across most of Kentucky, southern Illinois, southern Indiana and southern and eastern Ohio. Dry areas included southwest Missouri, western Iowa, northern Minnesota, southern and central Wisconsin, northern and central Illinois, northern Indiana, extreme southern Michigan, and northwest Ohio. Drought conditions lingered in Minnesota, Wisconsin, Upper Michigan, Indiana, and Ohio (Figure 5).
 

Hail and Thunderstorm Winds

The passage of the cold front on September 27th caused severe weather from Wisconsin to Ohio. Hail up to 1" was reported in Wisconsin, Illinois, and Indiana. Ohio was hit with hail up to 1.25". Thunderstorms winds also caused tree damage in those same states as well as in Michigan.
 

Strong Non-Thunderstorm Winds

Strong winds associated with the cold front on the 27th affected the northern Midwest. Gale warnings were issued for the Great Lakes, northern Indiana had warnings for flooding due to high waves, and Lake Erie water levels dropped from Toledo to Port Clinton as water was pushed to the east end of the lake. Water levels dropped enough for boats to get stuck in the muck at the bottom of the lake, flooding when the water returned.

The winds also caused widespread power outages from Minnesota to Ohio. More than 7,000 customers around the Twin Cities were affected. 13,000 were without power in the Green Bay area. Hundreds lost power in northern Michigan, the Grand Rapids area, and northwest Indiana. The winds even knocked out power during the Cleveland Cavaliers' Media Day in Independence, Ohio.
 

Flash Flooding

Thunderstorms brought heavy rain to northern Kentucky in the early morning hours of September 27th. Fast rising water forced evacuations at a trailer park in Nicholasville, Kentucky (Jessamine County). Minor flooding also affected south central Indiana on the 26th.
 

-MST-