Midwest Weekly Highlights - May 25-31, 2011
Cool Northwest, Warm Southeast
There was a sharp gradient in temperature departures this week across the Midwest (Figure 1). Temperatures were 9°F below normal in far northwestern Minnesota, to 9°F above normal in eastern Ohio. Near normal temperatures occurr4ed in a band from central Missouri northeastward through central Illinois and in the lower Michigan. The first three days of the period were much colder than normal over all but Indiana and Ohio (Figure 2), while the last four days of the month were much warmer than normal except for Minnesota, and from Iowa across northern Illinois. (Figure 3). There were a few record lows set at the beginning of the week, and numerous record high temperatures the last part of the week.
Rainfall was much above normal from western Minnesota south through northern Missouri, and eastward from Iowa and Missouri through the northern two-thirds of Illinois, northern Indiana, and southern lower Michigan (Figure 4). In contrast, precipitation was much below normal this week across the northern half of Wisconsin and southern Ohio. The rain did slow down spring planting, and had it not been for the rain corn planting would have been complete in a number of states. Planting in Ohio is still far behind the remainder of the Midwest and the five-year average. Except for Iowa, soybean planting is well behind the five-year average in the region.
More Severe Weather
For the second week in a row severe weather was widespread across the Midwest, especially the southern half (Figure 5). Most of the severe weather occurred on May 25th as a strong low pressure system moved east from the Central Plains (Figure 6). A stationary front draped across the central Midwest provided a focus for thunderstorm development. By early afternoon on May 25th a number of tornado watches were in effect from Missouri and Arkansas through Illinois, Indiana, and Kentucky. Before the day was over more than 25 tornadoes were reported in Missouri, Illinois, Indiana, and Ohio.
While most of the severe weather occurred on May 25-26, severe storms also occurred on May 28th and May 29th along and ahead of a warm front stretched across the Midwest (Figure 7). The greatest concentration of severe storms was on May 29th from southern Iowa across north central Illinois, northern Indiana, and southern lower Michigan. One EF1 tornado was confirmed in Michigan.
The month ended with summer-like warmth spreading across the region (Figure 8), with some scattered severe storms across Minnesota and Wisconsin ahead of a strong low moving northeast from the Northern Plains.