October 21-31, 2000:

The last week of October was dominated by dry and warm conditions in the Midwest. Only Minnesota, northwestern Iowa, and extreme southwestern Missouri received more than 1 inch of rain, but some areas of the central Midwest / Ohio Valley received less than 0.25 inches for the week. While the week started with some rain in Michigan and eastern Ohio on October 24 and 25, virtually no rain fell east of central Iowa the rest of the week, except for some light showers on the 27th (Figure 10). At the same time, temperatures were more than 9 Deg F above normal south of a line from southern Minnesota to eastern Kentucky, and at least a few degrees above normal elsewhere (Figure 11). The main reason for this surface weather pattern was the existence of a strong omega blocking pattern in the upper atmosphere over the United States (Figure 12, Climate Diagnostic Center). This pattern, shaped like the Greek letter Omega, resulted in a very strong upper level trough over the West Coast, a ridge over the Midwest, and another trough over the East Coast. While there were frequent and very heavy rains over the Great Plains, the individual low pressure centers could not reach the Midwest, instead moving northward into Canada and leaving this area warm and dry.