May 11-17, 2010
Midwest Weekly Highlights - May 11-17, 2010
Wet and Cold
A series of upper level troughs crossing through the Midwest brought wet, cold weather to the region this week. The entire region received much above normal rainfall except for the area that needs it most in the upper Midwest. The heaviest rain fell in the central Midwest, where precipitation was as much as four times normal in southern Iowa through northern Missouri and in southwestern Missouri (Figure 1). Precipitation was less than 10 percent of normal in the central Michigan Upper Peninsula. Small areas with less than 75 percent of normal rain occurred in northwestern Minnesota and along the Ohio in Illinois and Indiana. Moderate to severe drought continued to be depicted across northeastern Minnesota, the northern third of Wisconsin and from the northern tip of Lower Michigan across the Upper Peninsula (Figure 2). Wildfires broke out in the Michigan U. P. as warm and very dry weather further dried out vegetation, and crews were busy keeping them contained.
Average temperature departures varied by 12°F across the region. Along and south of the Ohio River, temperatures were from 1°F to 3°F above normal. Extreme northern Minnesota was near normal, but elsewhere northwest of the Ohio River temperatures ranged from 1°F to 4°F below normal in Ohio to 8°F below normal in western Iowa (Figure 3). There were many record low maximum temperatures and record high minimum temperatures set this week. Persistent clouds and rain kept daytime temperatures from rising, but also kept overnight temperatures from falling.
Heavy Rain Causes Many Problems
A frontal system stalled out over the southern Midwest (Figure 4) provided the focus for heavy rain the first three days of the period. This system produced heavy rain across central and southwestern Missouri as the front initially pushed into the Midwest on May 11. By the morning of May 12, 2.50 to 4.5 inches of rain had fallen in a narrow band across southwestern Missouri (Figure 5). With prospects for more rain, flood and flash flood watches were posted for most of Missouri, southern Iowa, and western Illinois (Figure 6). Later in the day, watches were extended across northern Illinois into northern Indiana and southern Michigan (Figure 7). The area of heavy precipitation shifted northward, and by the morning of May 13 two to four inches of rain accumulated from northwestern Missouri into central Iowa and western and northern Illinois (Figure 8).
Flooding of rivers and streams and flash flooding was widespread in the affected areas. Two people died in Missouri when their vehicles were swept away by floodwaters flowing over roads. Rising waters in the Mississippi River in St. Louis forced the President Casino to temporarily close until waters receded and debris could be removed from streets and parking lots. On May 13 in southern Iowa, Amtrak's eastbound California Zephyr had to be detoured because floodwaters had washed over the tracks near Ottumwa (Wapello County) and in Burlington (Des Moines County). More than five inches of rain flooded streets in Burlington.
Severe Weather
Severe weather was limited to the southern half of the region this week in the vicinity of the stalled front and the storm track. On May 13 five tornadoes were reported in the Midwest, with three in southwestern Missouri and one each in Indiana and Ohio. Severe thunderstorm broke out ahead of the front as it pushed south of the Ohio River on May 14, with numerous reports of hail greater than one inch in Kentucky. Golf ball to baseball sized hail (2.50 to 2.75 inches in diameter) was reported in Todd County.
-SDH-