September 1-7, 2010
Midwest Weekly Highlights - September 1-7, 2010
A Cool Start to September
September and meteorological fall began with a welcome break from the persistent heat and humidity of the summer. Two strong cold fronts moved through the Midwest this week, ushering in refreshingly dry air, but at the same time bringing some much-needed rain to parts of the Midwest.
Temperatures were normal to well below normal across the Midwest the first week of September. Average daily temperatures were near to 2°F above normal in Ohio, eastern Michigan, and eastern Indiana, but 6°F to 7°F below normal in western Minnesota (Figure 1). Record high minimum and record maximum temperatures were recorded the first three days of the week in the eastern half of the region, followed by record low maximums and record minimum temperatures after cold air spilled in on September 3.
Precipitation was much above normal this week across much of the northwestern two-thirds of the region, with parts of Missouri, Illinois, Wisconsin, and Michigan receiving three to five times normal rainfall (Figure 2). In contrast, rainfall was less than 25 percent of normal across much of Ohio, and little or no rain fell along and south of the Ohio River. The September 7 U.S. Drought Monitor eliminated Abnormal Dryness in Illinois and western Indiana as a result of the rain early this week. However, Severe Drought is now being depicted in the Missouri bootheel. There was little change in the far northern Midwest (Figure 3).
Corn and soybean harvest was underway with the dry weather and early maturation of the corn and soybean crop. Harvest of corn and soybeans began in the last week of August in Ohio, Indiana, and Illinois and accelerated with the dry weather this week.
Torrential Rain in Missouri
A strong upper level wave rotating south out of Canada drove a cold front through the Midwest on September 1-2. A wide band of showers and thunderstorms developed ahead of the front (Figure 4). The heaviest rain developed along the southern end of the front in southwestern Missouri. Five to ten inches of rain was recorded in the 24-hour period ending the morning of September 2 (Figure 5), with a 10.21 inch amount recorded by a CoCoRaHS observer near Ozark, MO (Christian County) (Figure 6). The heavy rain resulted in widespread flash flooding. More than 50 roads were closed due to high water in southwestern Missouri, and emergency crews were kept busy making numerous water rescues. Two locations set all-time daily records for precipitation in this event. Marshfield, MO (Lawrence County) received 6.67 inches of rain on September 2, breaking the old record of 6.17 inches set less than a year ago on October 9, 2009. Halltown, MO (Lawrence County) received 4.75 inches, breaking the old record of 3.55 inches on June 7, 1974
The cold front continued to press eastward and brought heavy rain to northwestern and central Illinois and northwestern Indiana. An inch of rain was common, but a number of locations in northern and central Illinois exceeded two inches of rain for the 24-hour period ending on September 3.
Cool and Blustery
Following passage of the cold front, much cooler and blustery weather remained over the Midwest. Strong west to northwest winds gusting in excess of 40 mph on September 3 knocked out power for over 13,000 customers in northeastern Wisconsin. The winds also forced closure of several rides at the Minnesota State Fair in St. Paul (Ramsey County).
As high pressure settled in over the Midwest on September 5 overnight low temperatures dropped into the mid 40s as far south as the Ohio river, and below freezing in some locations in northern Minnesota (Figure 7). Several locations in St. Louis County, MN recorded the first freezing temperatures of the season, with a low of 27°F at Brimson and Embarrass, MN (Figure 8).
A second cold front swept through the Midwest late on September 6 and on September 7, prompting high wind warnings and advisories to be posted for the northern portions of the Midwest (Figure 9). Winds gusts in excess of 40 mph (Figure 10) blew trees into power lines causing power outages across southeastern Wisconsin and lower Michigan. An 80 year-old man was seriously injured when he was struck by a tree limb in his back yard in Wauwatosa, WI (Milwaukee County). In Ludington, MI (Mason County) a man drowned when he was swept off a pier and into Lake Michigan by six to ten foot waves driven by the winds.
Only Scattered Severe Weather
Thunderstorms associated with the two strong cold fronts that moved through the Midwest this week produced scattered severe weather. No tornadoes were reported. Wind and water damage from overnight severe weather delayed the opening of the 2010 Farm progress Show in Boone, IA (Boone County) on the morning of September 1.
-SDH-