Midwest Weekly Highlights - April 24-30, 2011

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Downpours Soak Southern Midwest Again

The southern Midwest was already quite wet and it picked up several inches more during the last week of April. Southeast Missouri, southern Illinois, southern Indiana, and western Kentucky picked up 5+" of rain in seven days (Figure 1). Some of the highest totals were in southeast Missouri with totals exceeding 10" (18 Cooperative stations), including Poplar Bluff (Butler County) which recorded 15.87" of rain. There were 494 daily precipitation records set. Rainfall was in excess of 750% of normal in southeast Missouri and also well above normal across the eastern half of the region. Totals ranging from two to three times normal were widespread with some areas topping five times normal (Figure 2). Below normal precipitation totals were located along the western edge of the Midwest and extending along the Iowa-Missouri border into west central Illinois.
 

Temperatures Vary

Temperature departures were above normal southeast of a line from the boot heel of Missouri to the Ohio-Michigan border. The warmest departures neared 8°F above normal in parts of Kentucky and Ohio. To the northwest, departures were as much as 6°F below normal in northeast Iowa (Figure 3). Extreme northwest Minnesota was slightly warmer than normal. Daily temperature records were a mix of record highs and lows.
 

Deadly Outbreak of Tornadoes Extends into the Midwest

One of the worst tornado outbreaks in US history struck the southern US on April 26th and 27th. More than 340 people died in the storms, mostly on the 27th. Preliminary storm counts put the 2-day count of tornadoes over 300. The outbreak reached into the southeastern part of the Midwest, though the region was spared from the killer storms that struck Mississippi, Alabama, Georgia, and Tennessee. The tornado that hit Tuscaloosa and Birmingham, Alabama killed 65 people making it the deadliest single tornado since 1955. The nationwide death toll on the 27th, 334 fatalities, was the highest in over 85 years.

Following a couple days with severe weather the previous week, severe weather hit the southeastern Midwest for several days, April 24th through April 27th (Figure 4). Stalled frontal boundaries served as triggers for severe storms (Figure 5). Hail, wind, and tornadoes were reported in southeast Missouri, southern Illinois, southern Indiana, Ohio, and across Kentucky. Tornado reports (EF0 to EF2 rated) came from Missouri (Bollinger County and Scott County), Kentucky (Christian, Calloway, Lyon, Caldwell, Grayson, Hardin, Hopkins, Green, and Monroe Counties), Indiana (Warrick, Pike, and Hendricks Counties), and Ohio (Clark County). Hail 2" or larger was reported on the 26th in Indiana (Warrick County) and Kentucky (Ohio County and Marshall County). Wind reports were most numerous in Kentucky on the 25th and 27th with 40+ reports each day.

On the 26th there were also reports of hail from southwest Michigan to Saginaw Bay and a single EF0 tornado on the ground for just over 3 miles near Burnips, Michigan (Allegan County). Hail 2" or bigger fell near Grand Rapids, Michigan (Ionia, Kent, and Montcalm Counties).
 

Record Flooding in the Southern Midwest

Flooding continues to impact the southern Midwest. Flood crests continued to work south along the Mississippi River in Missouri and Illinois. Major flooding along the Ohio River and its tributaries has been caused by the recent heavy rains. As the two rivers come together, both in flood, communities in Kentucky, Illinois, and Missouri are threatened by record floods that are, or soon will be, higher than the 1937 flood crests. Cairo, Illinois (Alexander County), just a couple miles north of the confluence of the Mississippi and Ohio rivers, was evacuated as the Ohio River matched the 1937 flood level and forecasts indicated a rise of 3 to 4 feet still to come (Figure 6). The high water level has caused sand boils and sink holes to develop in the Cairo area. Slightly upstream near Paducah, Kentucky (McKracken County) the high water has closed roads and bridges as well as causing landslides.
 

-MST-