Midwest Overview - April 2009
Precipitation Above Normal
April was a wet month with most of the region receiving from 2 to 9 inches of precipitation (Figure 1). Minnesota, northwest Wisconsin, and a small part of northern Michigan had 1 to 2 inches while parts of Missouri, Illinois, Indiana, and Michigan received 6 to 9 inches. Precipitation exceeded normal by 50% or more from northern Missouri, through most of Illinois, to central Indiana. Southern Michigan and the western part of upper Michigan were also 50% above normal (Figure 2). Monthly precipitation records for April occurred at 16 stations across Missouri, Illinois, Indiana, and Michigan.
A spring storm on April 19 and 20 brought as much as 10 inches of snow to northeast Minnesota, upper Michigan, and northern Wisconsin. That snow, along with the snow on the ground at the beginning of the month, has melted away with the seasonal warming. Only extreme northeast Minnesota and a few scattered spots in upper Michigan still have snow on the ground.
Drought conditions in the upper midwest improved in April with the above snow and some rain late in the month. The area of severe drought has been scaled back in response to this welcome moisture. Southern Ohio dryness was also alleviated by rain in April.
For the month, temperatures were close to normal (Figure 3). The western edge of the region was slightly cooler with departures from the mean of more than 2°F. The largest departures were along the Iowa-Missouri border where temperatures reached about 4°F below normal.
The monthly temperature departures averaged out big changes from the first 20 days of the month to the last 10 days. For the first 20 days, temperature departures were near normal to the north and below normal elsewhere with Missouri averaging about 5°F below normal (Figure 4). During this period the region set many record lows, especially record low maximum temperatures. Then during the last 10 days of the month, much warmer conditions (Figure 5) were swept into the region on strong southerly winds. Temperature departures ranged from 3°F to 4°F below normal in northwest Minnesota up to 8°F above normal in northeast Ohio. A swath of more than 6°F above normal extended from the Ozarks in southwest Missouri up the Ohio River basin into Ohio. Hundreds of record highs were set, with many being record high minimum temperatures from April 25 to 27. A four-state area with departures of minimum temperature in excess of 15°F occurred on those dates (Figure 6).
Red River was in major flood for most of April. Coming off a record crest at Fargo in late March, the river level was dropping early in the month but then climbed back near record levels later in the month due to snow melt and rain. By the end of the month most locations along the Minnesota border had dropped below major flood stage.
Early in the month, flooding was a concern from northern Missouri to southern Michigan. Flooding in this area eased mid-month, with only the lower Illinois River still in flood, but flooding returned with heavy rains during the last week of April.
Severe weather in April included tornadoes reported on April 9 (MO), 10 (KY), 25 (MO), 26 (IA and WI), and 30 (KY). Hail over 2 inches in diameter fell in Missouri on April 9 and in Iowa and Wisconsin on April 24. Reports of hail and wind damage were also numerous on April 2, 5, and 13 in addition to the dates above.