April 4-10, 2001

During the week of April 4-10, the Midwest spent several days on spring and went right into summer. A stationary front draped across the Midwest most of the week, oscillating back and forth as several low pressure areas moved along it. Two of these storms were noted for their high non-convective winds caused by intense pressure gradients. Most of the region received more than one inch of rain, with several axes along storm tracks and the paths of mesoscale convective systems receiving 2-4 inches of rain (Figure 7). Minnesota, Iowa, and Wisconsin received 4-8 times their normal rain amounts (Figure 8). The threat of severe flooding came to the fore this week, especially along the Red River of the North, the Minnesota River, and the Upper Basin of the Mississippi River. There was a tremendous temperature gradient across the stationary front during the week, with temperatures only a few degrees above normal in the northern Midwest, while temperatures averaged 14-18°F above normal in the southern half of the Midwest (Figure 9). During the day on April 8, a number of places set temperature records, and the pattern of daily maximum temperatures looked like a typical June pattern (Figure 10 ). All of this warm weather brought about the rapid melting of snow packs in Minnesota, Wisconsin, and Michigan this week, leaving very little left on the 10th (Figure 11).