Midwest Overview - April 9-16, 2003

April 9-16 was dry over much of the central Midwest, with heavy precipitation restricted to Kentucky at the beginning of the period, and the northern Midwest at the end of the period. A wide swath through central Minnesota and Wisconsin received more than one inch of precipitation, while parts of southeastern Kentucky received over 7 inches of rain (Figure 1). Precipitation totals were generally well below 25% of normal elsewhere in the region (Figure 2). Temperatures turned much warmer half way through the period, with many maximum temperature records falling on the 14th in the western Midwest and more falling on the 15th in the central and eastern Midwest. However, the averages for the period were considerably less due to some cooler conditions earlier in the period, ranging from near normal to 5°F above normal over most of the region. Only in the western Midwest north of Missouri were temperatures 6 to 10°F above normal (Figure 3). The precipitation was welcome in Kentucky and the northern Midwest, locations that were drying rapidly. Unfortunately, drought intensified in areas of the central Midwest afflicted with little rainfall and several warm, dry, and windy days during the period (Figure 4, National Drought Mitigation Center).

As the period opened, the people of Oakland county, northeast of Detroit, Michigan, were still living with the damage of the previous week's ice storm. About 93,000 power customer were without power on April 9. By the end of April 11, this number had been reduced to 15,000, many of whom had been without power for a full week. The cost of the ice storm clean-up and recovery was estimated by Detroit Edison to be $40M in its service area, with more to be added elsewhere as damages in areas serviced by different utilities are counted. Meanwhile, in Kentucky, three days of rain fell on April 9-11 due to a very slow moving low pressure center passing to the southeast of the region. The welcome rains soaked into dry ground in most of the state. In the southeastern part of Kentucky, though, rain totals of seven inches were recorded at two observation sites, and five inch totals were widespread (Figure 5, National Weather Service). The Cumberland River at Williamsburg reached over 7 feet above flood stage before receding, rising more than 20 feet over its low level at the beginning of the rainy period (Figure 6), US Geologic Survey). Fortunately, not much flood damage was reported. The previously dry conditions allowed for such a tremendous rain event to have a relatively low negative impact.

Warm air started entering the Midwest beginning on April 13. A surface low drifted southward for a day in the Great Plains, setting up a strong pressure gradient with an eastern U.S. high pressure center on the 14th (Figure 7, U of Illinois Department of Atmospheric Science). A very broad area of the Great Plains and the western Midwest had temperatures in the mid- to upper 80s (Figure 8, UIUC DAS), and record high temperatures were set in more than 35 locations in the MRCC service region. The low pressure center finally started moving to the east on April 15, and about ten more temperature records fell in the central and eastern Midwest. During the day, the combination of warmth, low dew points, and high winds gusting to more than 40 mph created red flag wildfire danger conditions from the boot heel of Missouri to Minnesota and Wisconsin. The worst fire occurred along a five mile strip of railroad track in Oak Creek, a suburb of Milwaukee, WI. While the fire was probably triggered by sparks from a malfunctioning train car brake, the winds and warm and dry conditions quickly whipped it into a dangerous situation. More than 150 firefighters from 10 fire departments fought the blaze. Fortunately, the tracks were set back from local houses, but one house and part of a plant nursery were destroyed by the fire. Dozens of other fires were reported in southern Wisconsin that day, including one that consumed 600 acres of timber. Fires were a problem for several days prior to the 15th, with more than 120 grass fires reported in Minnesota alone during the period. Northern Illinois and Michigan also reported many fires, one requiring response from 21 fire departments near Antioch, IL, and one burning 800 acres in Wexford County, Michigan. Due to the drought preceding the warm, dry, and windy conditions, fuel moisture was dangerously low. During this drought year, 618 separate wildfires have occurred in Wisconsin.

Fortunately, significant rains developed along a stationary front draped across much of the northern Midwest. Unfortunately, strong storms also developed along the front in central Minnesota, Wisconsin, and Michigan late on the 15th (Figure 9, NWS), with heavy rain and some severe hail and wind reports in eastern Wisconsin (Figure 10, Storm Prediction Center). The rain helped in some areas, but missed much of the central Midwest areas that remained in a high fire danger situation. Dryness was still affecting Great Lakes levels. As the spring shipping season began, the first lake freighter to reach Holland, MI, delivered only 4,420 tons of limestone instead of the ship capacity of 5,400 tons, in order to maintain a draft of 17 feet rather than the normal 19 feet when entering the harbor. Marina owners are also reporting problems with some of their slips not having enough water depth to accommodate boats.

On the northern side of the stationary front, conditions were hazardous for another reason: freezing rain. The strong boundary separated air masses with a 30°F temperature difference. In Traverse City, MI, when the front slipped to the south, temperatures fell from 78°F to 48°F in only 22 minutes. Half inch ice deposits were found in northwestern Wisconsin, where there were isolated power outages that affected several hundred customers each. The combination of ice and high winds required the closing of several bridges in the area. There were also a large number of traffic accidents due to the changeable spring weather.