Midwest Weekly Highlights - July 18-24, 2010

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Heavy Downpours in Many Locations

The precipitation during the third week of July came in heavy downpours. Numerous locations were pounded by heavy rains that led to flash flooding. More than 400 daily precipitation records were set, along with 33 monthly records and eight all-time records. Precipitation totals exceeded 10 inches in parts of Iowa, Illinois, and Missouri (Figure 1). Though there were locations below normal, locations above normal were well above normal, exceeding 400% of normal in parts of all nine Midwest states (Figure 2). The driest areas were around Lake Superior, a swath from Illinois to Ohio, and a swath from southwest Missouri to western Kentucky.
 

Temperatures

Temperatures ranged from near normal in the northwest to as much as 5°F above normal further south and east (Figure 3). Most of the daily temperature records were record high minimum temperatures, many of which occurred on the 23rd and 24th as high dewpoints (Figure 4) kept the lows in the 70s, and even the upper 70s, in the southern half of the Midwest (Figure 5).
 

Flash Flood Fatalities in Missouri and Kentucky

Flash flooding was blamed for the death of a Missouri woman and a Kentucky woman during the week. The Missouri death occurred on the 20th when a woman slipped off of a flooded low water crossing near Louisiana, Missouri (Pike County). The Kentucky woman was swept away in her mobile home on the 21st near Fultz, Kentucky (Carter County) as rains of 3" to 5" covered the county and neighboring counties. Although her smashed home was located promptly, it took several days to find her body.
 

Rivers on the Rise

The heavy rains led to rising rivers in the Midwest (Figure 6). Though some rivers had already crested by the 24th, many were forecast to do so in the following few days. In some cases, rivers rose and fell repeatedly as the rains moved through over the past week or two. As of the 24th, flooding was still occurring across Iowa, northern Missouri, northern and western Illinois, and southern Wisconsin. The Mississippi River was flooding or approaching flood stage from Iowa to Missouri.
 

Severe Weather

Severe weather was widespread during the week (Figure 7). Thunderstorm wind damage was reported in all nine states and on all seven days. Hail reports were not as numerous, however golf ball sized hail fell in Lenawee County, Michigan on the 18th, seven Wisconsin Counties on the 20th, (Allegan County), Michigan on the 22nd, and Linn County, Iowa on the 23rd. Tornado reports came on six different days, all but the 24th, and from seven states, skipping only Kentucky and Ohio.
 

Flash Flooding in Many Locations

Heavy downpours led to flash flooding on several days during the week. On the 19th and 20th, northeast Missouri was hit with several inches of rain. Totals exceeded 2" over a large area including southeast Iowa and west central Illinois and radar estimates of over 6" extended from the southern edge of Iowa across multiple Missouri counties (Figure 8). CoCoRaHS observers in Missouri reported totals of 9.13" (Adair County) and 8.51" (Shelby County) on the morning of the 20th. Ten Cooperative stations in Missouri and seven additional CoCoRaHS stations exceeded 4" on the 20th. In Hannibal, Missouri (Marion County), two injuries were blamed on the flooding, more than 100 homes and businesses were damaged, and at a day care, 15 people had to be evacuated by boat. More than 30 water rescues occurred in Hannibal alone. Three major highways, U.S. 36, U.S. 61, and U.S. 63, and 60 other roads were closed in northeast Missouri due to high water. Flash flooding was also responsible for 911 outages in Corydon, Iowa (Wayne County) and some neighboring towns.

The 20th and 21st brought the big rains to northeast Kentucky. Several inches of rain fell across northeast Kentucky and neighboring Ohio and West Virginia (Figure 9). Due to hilly terrain, the runoff quickly swelled streams leading to flash flooding. In addition to the death in Carter County, there were many accidents, evacuations, submerged vehicles, and a roof collapse in Louisville, Kentucky (Jefferson County). Power or water outages affected thousands in Kentucky. Numerous roads were closed and at least two county bridges were damaged in northeast Kentucky. In Lewis County, Kentucky, seven homes were destroyed, 30 homes were damaged, and a grocery store was pushed off its foundation. The bridge on Highway 57 between Lewis County and Fleming County was flooded and parts of the roadway were washed away by floodwaters. Ironton, Ohio (Lawrence County) was also hard hit with reports of ruined homes and water more than six feet deep.

Overnight storms dumped several inches of rain in northwest Iowa on the 21st and 22nd (Figure 10). In George, Iowa (Lyon County), the Rio Grande Creek unleashed some of its worst flooding in years. More than 400 homes were flooded and three homes sustained structural damage when basement walls collapsed. Six of eight bridges in town and an estimated 500 miles of county roads were damaged. In addition to the flooding, Maurice, Iowa (Sioux County) was hit with extremely strong straight-line winds of 80 to 100 mph causing an injury, a destroyed home, several roofs blown off homes, many downed trees, and lots of downed power lines.

The evening of the 22nd was southern Wisconsin's turn to take on heavy rains (Figure 11). In Milwaukee, Wisconsin (Milwaukee County), torrential rains, up to 7" in just a couple hours, overwhelmed drainage systems. The flooding shut down numerous roads including Interstate 43 and U.S. 45. The airport was shut down and did not reopen until the 23rd. More than 50 people were rescued from homes or cars including three rescues that included dive teams. A sinkhole opened up in an intersection on the north side of town, swallowing a vehicle and occupant who was rescued and sent to an area hospital. Two people were struck by lightning. Manhole covers were blown off and at one location water was spouting 5 feet in the air. Tens of thousands were without power from the storm. Sewage was released into rivers and Lake Michigan as the combined storm and sanitation sewers were overwhelmed. The Milwaukee Public Schools cancelled all programs on the 23rd because of water in several school buildings.

Heavy rains fell in northeast Iowa, southwest Wisconsin, and northwest Illinois on the 22nd and 23rd (Figure 12). Storm totals exceeded 10" in parts of Iowa, more than doubling the normal July totals in just two days. Grant County, Wisconsin had widespread damage to roads and bridges and its water treatment plants were also flooded. Infrastructure damages totaled more than $100,000 in at least three towns. Many roads in northeast Iowa and northwest Illinois had to be closed due to high water. An historic old iron bridge was washed away near Elizabeth, Illinois (Jo Daviess County). In Savanna, Illinois (Carroll County), the Plum River burst through a railroad dike flooding homes, washing away rail cars and tracks, and washed away land under the Illinois 84 bridge that connects the north and south sides of town. In Stephenson County, Illinois, the Pecatonica River and Yellow Creek flooded damaging an estimate 1,000 residences. The Maquoketa River in Iowa swelled to nearly three feet above its previous record crest and more than 10 feet above flood stage. About 4000 acres of farmland were flooded in Delaware County. The situation worsened when the earthen dam, which dated back to the 1920's, at Lake Delhi (Delaware County) failed on the 24th. Water topped the dam, eroded away what eventually became a 200-foot breach through the dam, and drained the entire 450-acre lake. Both Monticello and Hopkinton were evacuated downstream as dozens of homes and businesses were flooded along with the sewer treatment plant in Monticello. The Wapsipinicon River in Jones County, Iowa also flooded roughly 4000 acres of farmland.

Overnight rains pounded Chicago, Illinois (Cook County) and surrounding communities on the 23rd into the 24th (Figure 13). More than a month's worth of rain fell overnight in many locations with totals of 5 " to 8" at several CoCoRaHS stations (Figure 14) in Cook, DuPage, and Kane Counties. Fifty CoCoRaHS stations reported 5" or more across northern Illinois with the highest report of 8.20" in Glen Ellen, Illinois (DuPage County). Midway Airport reported over 7.5" and O'Hare Airport reported more than 6.3". The water overwhelmed the combined sanitary and storm sewer system causing the release of untreated water into Lake Michigan closing all beaches in the city for several days. Interstate highways and mass transit trains were shut down for hours by high water. Homes were flooded in the city and suburbs with Westchester (Cook County) particularly hard hit. More than 40 underpasses were flooded in Chicago and 150,000 ComEd customers were without power at the peak of the storm.
 

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