Midwest Weekly Highlights - September 1-9, 2009
Precipitation for the first nine days of September ranged from more than 200% of normal to no rain at all (Figure 1). A large swath from eastern and central Iowa to northern Michigan received no rain during this period. Heavier than normal rains fell across the southern Midwest, extreme western Iowa, and northwest Minnesota. Drought continued to affect areas from Minnesota to Upper Michigan including the northern half of Wisconsin (Figure 2). Pockets of severe drought remain in all three states while abnormally dry conditions developed in regions of Iowa, Indiana, and Ohio.
The month began with the Midwest under the influence of a broad area of high pressure (Figure 3). September 1st and 2nd were well below normal with temperatures in Missouri to as much as 14°F below normal (Figure 4). Over a hundred record low temperatures were set this week with most occurring during those first two days.
Temperatures averaged below normal for the first nine days of the month across most of the Midwest (Figure 5). Above normal temperatures only occurred in northern Minnesota and Upper Michigan with below normal temperatures elsewhere. The largest negative departures were in western Missouri (-9°F) and the largest positive departures were in northwest Minnesota (+5°F).
Iowa river flooding in southeast Iowa (Louisa and Des Moines counties), caused by heavy rains at the end of August, abated early this month allowing the re-opening of county roads. High Mississippi River levels during the week have delayed attempts to fix a sewer line that has been leaking sewage into the river near Burlington, Iowa.
Late in the week, flash flooding hit the southern Midwest as an upper air disturbance brought heavy rains to the area. 134 daily precipitation records were tied or set from September 6th to 9th. Flash flooding was reported in northern Kentucky and the Cincinnati metro area on the 8th as 2-3" of rain fell in the early evening.
Severe weather largely missed the Midwest during the week. Nearby states to the west and south reported severe weather on several days but the Midwest only logged reports in eastern Kentucky on the 8th and Ohio on the 9th. The Kentucky reports included both hail and wind damage while the lone Ohio report was for wind damage.