Midwest Weekly Highlights - April 24-30, 2007
Soaking Rains in the Central Midwest
A strong and slow-moving weather system brought heavy rain and several days of inclement weather to the large portions of the Midwest the last week of April.
Rainfall was heavy this week across the central Midwest (Figure 1), generally four to five times what would normally be expected (Figure 2). The rainfall pattern reflected the path of the storm and the front that bisected the region. However, north and south of this band, it was rather dry with central Minnesota to northwestern Wisconsin receiving little or no rainfall. It was also dry from southern Illinois across southern Kentucky, where rainfall ranged from less than 50 percent to 75 percent of normal. The dry weather in the upper Midwest resulted in Moderate Drought spreading back into northwestern Wisconsin on the latest U.S. Drought Monitor (Figure 3).
The temperature pattern also reflected the path of the low pressure system this week. The coolest weather was found along the storm track from western Missouri across northern Illinois and southern lower Michigan (Figure 4), where temperatures ranged from 1°F to 2°F above normal. In northern and southern portions of the Midwest where there was a lack of rain and clouds, temperatures ranged from 5°F to 8°F above normal.
Heavy Rain Results in Flooding, Planting Delays
A low pressure system was developing over the Oklahoma panhandle on the morning of April 24, with a front extending eastward from the low through the Ohio Valley (Figure 5). For the next four days a series of low pressure waves traveled along this frontal boundary producing heavy rain and scattered severe weather. Most of the rain fell from late on April 24 through April 25. The first wave of precipitation came late on April 24 and during the early morning hours of April 25 as showers and thunderstorms developed rapidly along and south of the frontal boundary across Missouri and in Iowa as the front lifted northward. Two to four inches of rain fell from north-central Iowa eastward across north-central Illinois into northwestern Indiana (Figure 6). Severe thunderstorms in Missouri resulted in flash flooding and caused some straight-line wind damage.The heavy rain in Iowa, in particular, caused flooding on a number of rivers and streams. The Iowa River, the Skunk River in Ames, and the Racoon River in Des Moines all rose above flood stage. The flooding resulted in a number of road closures but no major damage. The heavy rain in northern and central Illinois kept the lower Illinois river in flood through the end of the month.
There was a break in the rain during the morning and early afternoon of April 25, but as the atmosphere heated up thunderstorms began erupting across eastern Missouri and western Illinois. During the mid to late afternoon a number of the storms in the vicinity of the frontal boundary produced several funnel clouds and weak tornadoes (Figure 7). At least four touchdowns were reported in central Illinois, but there was little to no damage according to storm reports. The storms continued to develop into northern Illinois and Indiana during the evening hours. Heavy rain triggered flash flooding in northern Illinois and northwestern Indiana, with more than 18 inches of water reported over some roads. Flash flood watches were posted for much eastern Iowa and for northeastern Illinois in anticipation of more rain to come (Figure 8).
Another wave of low pressure moving along the frontal boundary set off another round of thunderstorms on April 26, with some severe weather across northern Illinois and Indiana, Ohio, and central Kentucky. Several tornadoes were confirmed by the National Weather Service in northern Illinois, northern Indiana, southern Ohio, and northern Kentucky (Figure 9). While one of the tornadoes in northern Indiana destroyed a barn and caused one injury, most damage from the twisters was minor.
The last low pressure wave finally pulled out of the Midwest on April 27, with the trailing showers and thunderstorms producing heavy rain in northern lower Michigan (Figure 10). Alpena, MI received 1.22 inches of rain, a new record for the date. The old record was 1.09 inches in 1995.
Spring Planting Behind Normal Pace
A period of warm, dry, and breezy weather the end of the third week of April continued into the early part of this week in the eastern portions of the region, and producers took full advantage of the favorable conditions to make some progress in corn planting prior to the onset of rain late on April 24. As of the end of the month. corn planting is about 17 percent behind the 5-year average for the nine-state Midwest region due to the cold weather in April and the recent heavy rain in portions of the Midwest.
Sunny, Warm End
Most of the Midwest enjoyed a sunny, warm end to the month of April. A band of showers and thunderstorms developed in northern Illinois along and north of a warm front late on April 29, and then continued on April 30 from southern Minnesota across central Wisconsin southeastward into Ohio (Figure 11). A few severe storms with small hail were reported in Minnesota, Wisconsin, and Indiana. Temperatures soared into the well into the 80s and even hit 90°F in a few locations on April 29 (Figure 12). On April 30 abundant sunshine south of the front (Figure 13) helped push temperatures well into the 80s with a few locations in the low 90s (Figure 14). A few temperature records were tied or set on both April 29 and April 30.