Midwest Weekly Highlights - April 1-7, 2009

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Storms Continue to Move Across the Region

The first week of April saw a continuation of the late March pattern, with a series of storms crossing the region. On April 1, a low pressure center lifted out of Minnesota into Canada as the associated cold front swept out of the region to the east. From April 2 to April 3, a low moved from Arkansas up the Ohio River valley bringing rain to the southeastern part of the region. A third low tracked across the region from Missouri to Ohio on April 5-6. This storm left a trail of new snow across southern Minnesota, northern Iowa, Wisconsin, northern Illinois, extreme northern Indiana, and into southern Michigan (Figure 1).
 

Variable Conditions Across the Region

Temperatures for the week ranged from near normal on the northeastern edge of the region to ten degrees below normal on the western edge (Figure 2). The week ended with temperatures below normal across the region, reaching as much as 12°F to 15°F below normal to the southeast and southwest.

The eastern half of the region saw above normal precipitation, with the Illinois-Indiana border exceeding 300% of normal. The western half of the region was quite variable. Small areas of high precipitation in Minnesota and Iowa were scattered among a generally drier pattern extending from Missouri through upper Michigan (Figure 3). Drought conditions remained in effect from southeastern Minnesota through northern Wisconsin and into upper Michigan (Figure 4). 
 

Flooding Continues

Major flooding (Figure 5) continues on the Red River at Fargo and downstream at Oslo and Drayton. River levels are receeding but snow on the ground from the past two weeks' storms threatens to push levels back up in the coming weeks. Moderate flooding (Figure 6) continues along the rest of the Red River and also at Montevideo on the Minnesota River, along the Illinois River, and in Indiana along the Kankakee River.
 

Severe Weather in the South

The National Weather Service changed the criteria for severe storms based on hail size. From April 1 onward, hail will need to be greater than or equal to 1" in order for a storm to be classified as severe (3/4" was the old limit). April 2 hail reports met the new severe criteria in western Kentucky (1"), southern Illinois (up to 1 3/4") and northwestern Ohio (1"). On April 4, large hail was reported in western Missouri (up to 1 3/4"). April 5-6 saw heavy wet snow bring power outages to Iowa, Indiana, and Michigan. A 12 mile stretch of I-35 in Iowa was briefly closed on April 5 due to heavy snow and multiple tractor trailer accidents. To the south of the low pressure on April 5, strong thunderstorms erupted leading to numerous reports of hail and wind damage in Kentucky and the neighboring counties.

MST