Midwest Overview - April 2011

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Lots of April Showers

Rainfall totals were above average for most locations in the Midwest. Monthly totals were two to four times normal in southern Missouri and eastward along the Ohio River (Figure 1). Precipitation totals for April set monthly records at 49 long-term (90 years of records or longer) stations. Monthly precipitation totals at seven of these locations topped the wettest month on record (Figure 2). Poplar Bluff, Missouri (Butler County) recorded an amazing 21.36" for the month, much of it falling in a six day run from April 22nd to 27th. More than an inch fell on each day, accumulating 18.10" over the 6-day period. Over 1000 daily precipitation records were recorded in April. The deluge of rain (Figure 3) caused widespread major flooding across the southern Midwest (Figure 4).

Although the last of the winter snow pack melted away during the first half of the month, new snow continued to fall in the upper Midwest (Figure 5). Light snows fell on the first five days of the month across the upper Midwest. Then on the 15th snow fell in northwest Minnesota and spread snow south to Iowa and east to Michigan through the 23rd. The area around Lake Superior picked up a couple more inches of snow on the 27th and 28th. Monthly totals topped 15" at Marquette, Michigan (Marquette County), 10" at Duluth, Minnesota (St. Louis County), Green Bay, Wisconsin (Brown County), and Alpena, Michigan (Alpena County), 6" in northeast Iowa, and even an inch or two in the Chicago area (Cook County).
 

Temperatures Varied in Time and Space

The first half of the month was above normal across the Midwest but the second half of the month was below normal for the northwestern two-thirds of the region while Kentucky and southern Ohio remained warm (Figure 6). Maximum temperatures were particularly cool in the latter half of the month averaging 10°F to 13°F below normal in Iowa, Minnesota, and Wisconsin (Figure 7). For the month as a whole (Figure 8), temperatures were above normal (up to 5°F) south of a line from Kansas City, Missouri (Jackson County) to Toledo, Ohio (Lucas County). To the north of this line temperatures averaged below normal (-1°F to -3°F). Some record high daily temperature records were recorded early in the month but gave way to mostly record low maximum temperatures later in the month.
 

Flooding a Big Story in April

Flooding was a big story throughout the month. Early in the month, major flooding was affecting the Red River in western Minnesota. Other rivers in Minnesota were also flooded as the last of deep winter snow pack melted over partially frozen and saturated soils. Flood conditions fell short of some predictions due to relatively dry and cool March weather which spread the spring melt out over a longer than normal time. The waters in the Mississippi River basin moved south causing serious flooding all along the Mississippi River. By late in the month the flood crest was primarily along the Missouri-Illinois border. The timing of this flood water was not good as it reached the confluence with the Ohio River as that river rose to record heights in Cairo, Illinois (Alexander County). The heavy rains of April 21st to 28th in the Ohio River valley led to major flooding on numerous tributaries of the Ohio River which then swelled the Ohio and led to the record flooding near Cairo (Figure 9) where the 1937 record was equaled as April came to an end.
 

Severe Weather Batters the Eastern Half of the US

April was one of the hardest hit hit month's in US history (Figure 10). Tornadoes and other severe weather caused hundreds of deaths, injuries, and untold destruction. The deaths were concentrated in the southern states on the 27th. The outbreak on the 25th to 27th is historic for by several measures. The number of tornadoes on a single day, 190 on the 27th, and the number over the three days, 305, are both unprecedented topping the 148 tornadoes in the April 3-4, 1974 outbreak. The death toll of 309 on the 27th ranks as the fifth deadliest day for tornado fatalities. The 65 deaths from the Tuscaloosa-Birmingham tornado along its 80 mile track rank as the deadliest single tornado since 1955.

Though the Midwest was spared the fatal twisters, damage was widespread from southern Missouri to Ohio and throughout Kentucky. Earlier in April outbreaks also occurred on the 4th and the 19th (Figure 11). The time series plot from the Storm Prediction Center showed number of severe weather reports off the chart on the the 4th (999), the 19th (738), and the 27th (705).

The event on the 4th was one of the busiest for severe weather reports in at least a decade. It was mostly in the southern states but extended to cover most of Kentucky as well. Damaging thunderstorm winds were the predominant report but 10 counties in Kentucky also reported tornado touchdowns. On the 19th, the severe weather hit the southern half of the Midwest and into the neighboring states to the south. Thunderstorm winds, hail, and tornadoes caused damage across a large swath of the region. Numerous tornadoes, rated EF0 to EF2, touched down in several states. Large hail, 2"+, and thunderstorm winds in excess of 80 mph were also reported in multiple states. Tens of thousands lost power from Missouri to Ohio.

A few other days had notable severe weather in the Midwest. Iowa was hit with multiple tornadoes on the 9th and Wisconsin was likewise hit on the 10th. More tornadoes on the 15th struck in eastern Missouri, central and southern Illinois, and western Kentucky. Leading up to the outbreak on the 27th, the southern Midwest had daily bouts of severe weather, including tornadoes, from southern Missouri to Ohio and Kentucky.
 

Field Work and Planting Held Up by the Weather

Field work and planting by Midwest farmers were making only sporadic progress on field work and planting in early April but heavy rains in the south and cold temperatures and wet soils in the north brought that to a near standstill for the latter part of the month. Corn planting, for example, was 20% to 45% behind the 5-year average in all nine Midwest states. Replanting is also likely, especially in Missouri, due to standing water in previously planted fields.
 

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The Iowa Climatology Bureau also contributed to this report.
The Minnesota State Climatology Office also contributed to this report.
The Missouri Climate Center also contributed to this report.