July 11-17, 2001

The week of July 11-17 was very dry in most of the Midwest, with a large swath through southern Minnesota, eastern Iowa, north and central Illinois, southern Indiana, and central Kentucky receiving no rain (Figure 12). This meant that cumulative precipitation anomalies increased from 0.5 to 1.5 inches in just one week in these areas (Figure 13). Only in Missouri and the northern Midwest were there heavy rains. The western two-thirds of Missouri exceeded 200% of normal (Figure 14), due to strong convective activity at the beginning of the period on July 11 and 12. Missouri, in fact, was the exception to the rule this week, and was the only state with overall increases in good / excellent quality categories of 5% or more for both corn and soybeans. Late in the period, the high pressure dominating the Midwest weakened, and storms started slipping around the Great Plains ridge into the northern Midwest. Heavy rains fell in western Wisconsin on July 17 associated with a mesoscale convective system, and much more widespread precipitation happened overnight at the end of the period, and will be included in next week's summary. Despite the usual association of dry conditions with heat in mid-summer, the dry areas of the Midwest were in fact dominated by a Canadian high pressure center most of the week. Temperatures were 2-6°F below normal over most of the Midwest (Figure 15). Towards the end of the period, though, a ridge built eastward from the Great Plains to the central Midwest, bringing very warm air at a time when crops were undergoing heat-sensitive fertilization processes.