Midwest Weekly Highlights - April 17-23, 2007

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Has Spring Finally Sprung?

The transition to a more stable temperature regime began this week across the Midwest. The northwestern half of the region experienced temperatures as much as 6°F to 7°F above normal. Along and south of the Ohio River, temperatures were still below normal, ranging from near normal from central Missouri to northwestern Ohio, to more than 2 °F below normal over central Kentucky (Figure 1).

Precipitation was generally scarce this week, with most of the region receiving little to no rain (Figure 2). The exception was the northwestern three-quarters of Minnesota, which received two to three times the normal weekly rainfall. The dry weather was welcome in much of the region, as spring planting delays were beginning to mount in the wake of the cool, wet spring so far. The rain in Minnesota helped chip away further at the drought that has been on-going since last summer (Figure 3). Despite the lack of rain, minor flooding continued in Illinois along the lower Illinois River.

 

A Week Without Much Excitement

Most of the rain that fell this week came during the last half of the period. A cold front triggered showers and thunderstorms in Minnesota on April 20 and April 21, resulting in a few reports of severe weather on both days, mostly from hail. An intensifying low pressure system located in western Kansas (Figure 4) resulted in more thunderstorms, a few of which became severe in southern Minnesota and southeastern Iowa on April 22. It was this weather system that also produced the heavier rain over Minnesota and Iowa. The thunderstorms weakened as they continued east into Illinois, Indiana, and Ohio on April 23, producing as much as 0.25 inch in some places, but with most amounts under 0.10 inch.

The intensifying low pressure system helped pull warm air well north into the Midwest, with highs in the 80s reported as far north as the Michigan Upper Peninsula on April 22 (Figure 5). Slightly cooler air filtered into the northwestern half of the region behind the cold front associated with the low on April 23, but high temperatures still remained well above normal for this time in April (Figure 6). Gusty winds affected much of the Midwest, with winds gusting as high as 45 to 50 mph over Wisconsin, southwestern Michigan, and northern Indiana.

SDH