Precipitation Percent of Normal
Total Precipitation
Total Precip Percent of Mean
Temperature Departures

Midwest Weekly Highlights - September 17-23, 2009


Precipitation

The third week of September brought a large weather event to our south. A slow moving area of low pressure pulled moisture from the Gulf of Mexico leading to torrential rains and deadly flooding across the Southeast US (Figure 1). The northern extent of the Gulf moisture extended into Kentucky, southern Indiana, and southern Missouri bringing widespread rainfall totals exceeding 3 inches (Figure 2). The rest of the Midwest was relatively dry with less than a half inch of rain falling in large parts of Minnesota, Wisconsin, and Upper Michigan.

Rainfall was much below normal (< 25%) in parts of Minnesota, Wisconsin, Upper Michigan, and eastern Ohio and much above normal (> 200%) in the southern third of the Midwest. Above normal precipitation also fell in extreme west central Minnesota and along a narrow swath from St. Louis, MO to Madison, WI to Alpena, MI (Figure 3). On September 21, Jacksonville, IL (4.73 inches) and Hazelton, IN (4.50 inches) both set all-time records for daily precipitation.
 

Temperature

Warm temperatures were the rule for the Midwest during the week. Temperatures ranged from near normal in western Missouri to 7°F above normal in Kentucky and as much as 14°F above normal in northern Minnesota (Figure 4). Temperature records for the week include at least one high and low of maximum and minimum temperatures, but most of the records were record high minimum temperatures occurring late in the week.

Warm weather and the lack of frost allowed crops to make rapid progress on maturity. Avoiding a frost remains important as crop development is still behind the 5-year average across the Midwest. Although harvest has begun in some early planted fields, most of the harvest will be late this year.

After the cool summer, Minnesota weather stations are experiencing their longest run of above normal daily temperatures for the 2009 season. In fact, September is on pace to challenge for the warmest in the state's recorded history.
 

Drought

The warm temperatures in the northern Midwest, combined with continuing dry conditions, led to a degradation of the drought conditions according to the September 22nd Drought Monitor (Figure 5). Severe drought now extends from east central Minnesota, across northern Wisconsin, and into Upper Michigan. Extreme drought extends from just north of Minneapolis into northwest Wisconsin. Drought conditions have also emerged in extreme northern Iowa, east central Indiana, and west central Ohio.

The drought conditions have led to extremely low soil moisture in southeast Minnesota (Figure 6). University of Minnesota researchers reported the lowest mid-September soil moisture content on record. Precipitation deficits in this area exceed 10 inches for the past 6 months (Figure 7).
 

Severe Weather

September severe weather returned to the Midwest with a tornado in Indiana on September 20th and both wind damage and large hail in Missouri on the 21st.

The Indiana tornado, located to the north of Borden (Clark County), was classified as an EF1 with winds estimated at 90 to 95 mph. The tornado was about 35 yards wide and was on the ground for approximately 3/4 of a mile according to the Louisville, KY NWS report.

Missouri severe weather included 1 inch hail in Benton and Polk counties and wind damage to trees and power lines in St. Clair County. The weather occurred on the north edge of a system that also brought severe weather to Oklahoma and then Arkansas.
 

Flash Floods

Localized heavy rains near Monett, Missouri (Barry County) led to flash flooding of Kelly Creek. NWS reports estimate that over 9 inches of rain fell in a few hours on the evening of September 19th. A mobile home park was evacuated, an estimated 70 businesses were damaged, and numerous roads were submerged by the swift moving water.

Southern Indiana was struck by flash floods on September 20. Rainfall totaled 5.77 inches in Clarksville, IN and flash flooding was reported in Clark, Harrison, Jefferson, and Floyd counties. In Charlestown, IN the high school and many homes were flooded and their misery was compounded by a long overnight power failure. In Clark and Floyd counties, stranded motorists were rescued and homes had to be evacuated.
 

Clouds of Bugs

A massive migration of soybean aphids brought out clouds of bugs in northern and central Illinois. Those outside to walk, bike, or enjoy an evening sporting event have been swarmed by the small gnat-like bugs. The bugs were so thick at times that it was difficult to avoid breathing them into one's nose.

The aphids move out of soybean fields in the fall and this year there have been more aphids than ever in Illinois. The cool summer weather is thought to have increased their numbers further to the south than normal. Although the migration is expected to last several weeks, the worst will likely be over in a week or two.
 

-MST-
The Minnesota State Climatology Office contributed to this report.
The Indiana State Climate Office contributed to this report.

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