March 25-31, 2007
Midwest Weekly Highlights - March 25-31, 2007
Unseasonably Warm Week Ends March
The entire Midwest experienced temperatures that averaged well above normal this week (Figure 1). The warm "bulls eye" was the central Midwest, where temperatures averaged 16°F to more than 18°F above normal from western Iowa into the Ohio Valley. The abnormally warm weather combined with occasional rain accelerated the climb in soil temperatures, and lawns were greening and trees were budding by the end of the month.
Rainfall this week was well above normal west of the Mississippi River, and much below normal east of the Mississippi (Figure 2). Rainfall was two to six times normal in the upper Midwest where drought has been persistent since July 2006 (Figure 3). At the end of the month the last vestiges of winter remained in the upper Midwest, where several inches of snow still covered the ground in northwestern Minnesota and over the eastern Upper Peninsula of Michigan (Figure 4).
Temperature Records Fall Like Dominoes
The week began with high pressure along the east coast combining with a low pressure moved in the northern to produce strong southerly flow over the Midwest (Figure 5). High temperatures on March 25 reached 80°F as far north as southern Minnesota and central Wisconsin (Figure 6). Numerous record high temperatures were set across the region on March 25, but that was only a prelude to what was to follow. The abnormally warm weather continued on March 26, and high temperature and high minimum temperatures were shattered throughout the Midwest. A few more records were set on March 27th, and cloudiness and precipitation associated with a cold front prevented the setting of more records.
Slow-Moving Fronts Bring Rain, Some Severe Weather
Showers and thunderstorms this week were associated with a series of frontal systems in the Midwest. There were a few reports of severe weather in Wisconsin and Michigan as thunderstorms developed ahead of the warm front on March 25. On March 27 severe weather was limited to a few hail reports in Michigan, although a tornado briefly touched down in Lawrence County, MO. Scattered thunderstorms in Illinois on March 28 spun up a tornado that touched down in Logan County but caused no damage. On March 3, scattered severe storms were reported in southern Missouri, southern Illinois and Kentucky.
An intensifying low pressure system located over southeastern Nebraska on the morning of March 31 produced the most widespread outbreak of severe weather of the week (Figure 7). The severe thunderstorms were concentrated along and north of a frontal boundary draped across southern Iowa and central Illinois. A squall line developed in Iowa during the late afternoon and moved eastward into Illinois (Figure 8). Hail to 1.75 inches was reported in Iowa, and there were numerous reports of damaging thunderstorm winds. In Illinois there were several reports of winds gusting to 70 mph, and one report of a gust of 80 mph in Kane County. In the McHenry County town of Marengo, winds damaged several apartment buildings, injuring 11 people. A microburst with winds estimated at 95 to 105 mph in Carol Stream and Glendale Heights, IL (DuPage County) caused damage to an apartment complex.
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North of the low pressure center, 1.00 to 1.50 inches of rain fell across south central Minnesota and in central Wisconsin (Figure 9).
Flooding Concerns Linger
Flooding continued on a number of rivers in the Midwest this week, most generally related to the aftermath of winter - snow melt combined with spring rains (Figure 10). However, heavy rain from thunderstorms was also responsible for flash flooding. In Michigan, an estimated 3 to 6 inches of rain from thunderstorms on March 27 in Chesterfield Township (Macomb County) produced flash flooding that caused extensive damage to as many as 100 residences. The rising Muskegon River in Osceola County forced the evacuation of some families in Evart. In Minnesota, lowland flooding occurred along the Long Prairie River in the central part of the state. During the week, minor flooding occurred along the Mississippi River from Clarksville to Elsberry, MO. The Illinois River continued to rise this week, cresting at slightly above moderate flood levels from Peoria to Havana and flood warnings were in effect. Flooding was also occurring on the Wabash River (Illinois/Indiana) and other smaller rivers in Illinois and Iowa.
SDH