September 5-11, 2001:

The period of September 5-11 began with several dry and temperate days, as the Midwest was dominated by high pressure at the surface and a ridge at upper levels. A deep trough dug southward over the western U.S. and then moved over the Midwest during the rest of the week, bringing copious rain and severe weather. Rain for the week exceeded 3 inches in southwest Missouri, central and northwest Iowa, and most of Wisconsin (Figure 10). Large sections of Indiana and Michigan received more than 2 inches of rain, and all but the eastern parts of Ohio and Kentucky received above normal rain (Figure 11). Most of the area was also above normal in temperature by 1-4°F, except for Iowa and northern and western Missouri, which were near normal to slightly below (Figure 12). Late on the 6th, the eastern portion of the trough edged into Minnesota and Iowa, bringing the western Midwest into a very active zone of the jet stream. With each upper level disturbance passing, considerable rain and thunderstorm activity took place. Moderate rain fell in Minnesota, Iowa, Wisconsin, and northern Illinois on the 7th, with much heavier rain over Iowa, southwestern Minnesota, and Wisconsin by the 8th. The very slow moving system brought heavy rain to the base of the trough late on the 8th in southern Missouri, and then started to move more quickly eastward, bringing heavy rains to central Kentucky, Indiana, western Ohio, and Michigan on the 9th as another disturbance passed from south to north along the exaggerated trough. No rain reached eastern Kentucky and Ohio, as the disturbance lifted northward, but the cold front did clear the rest of the region later on the 10th. The next cold front entered the region on the last day of the period, with a clipper system bringing light rain to the northern Great Lakes region. Topsoil rated as being short/very short of moisture fell 18% in both Missouri and Iowa. However, Great Plains states continued to have s/vs topsoil moisture ratings of 48-80%, despite some improvements. Areas rated as abnormally dry in the U.S. Drought Monitor have increased in the Great Plains, but were reduced in Iowa and eliminated in Minnesota by the rain (Figure 13).