Midwest Weekly Highlights - April 17-23, 2013

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Heavy Precipitation Leads to Several Rivers at Flood Stage

A rainy week brought above normal precipitation to a majority of the region, with at least 200% of normal precipitation spanning most of the Midwest (Figure 1). The largest departures of 500% to 750% of normal are found across southern Iowa and into northern Illinois, which was mainly a result of a heavy precipitation event on April 17th and 18th (see summary below). Precipitation totals ranged from very little precipitation in northwest Minnesota to pockets of 6" to 8" in Illinois, Iowa, Missouri, and Indiana (Figure 2). Just over 600 daily precipitation records were set throughout the week.

As a result of the rain that began on April 16th, at least ten USGS stream gauges in Illinois that have more than 20 years of record, have measured the highest flood levels ever recorded. As of April 22nd, more than 200 gauges were in flood stage along rivers in the upper Midwest, including 43 in "major" flood stage (Figure 4). The Significant River Flood Outlook from the National Weather Service indicates that much of Illinois, central Michigan, western Minnesota, and along the Wabash River already has significant flooding occurring or imminent and the possibility for significant flooding on the outskirts of these regions.

Record Breaking Snowfall

Portions of the upper Midwest received 7.5" to just over 20" of snowfall during the week (Figure 3), which is several inches above normal for this time of year in some locations (Figure 5). Totals in the upper Midwest during an event on April 18th and 19th include 7.2" at the Twin Cities International Airport in Minnesota (Hennepin County), 17.7" at the Duluth, MN airport (St. Louis County), and 22" near Two Harbors, MN (Lake County). Click here for more information on this late April snowstorm from the Minnesota Climatology Working Group. Another event later in the week (April 22nd and 23rd) brought several more inches of snowfall to portions of Minnesota, northern Wisconsin, and Upper Michigan (Figure 6). Several daily snowfall records were set during the week, in addition to a few monthly records and two all-time snowfall records in Elk River, Minnesota (Sherburne County) and Isle, Minnesota (Mille Lacs County). Some locations in the upper Midwest are on their way to having April 2013 rank in the top 10 snowiest Aprils on record. Click here for more information on why there has been so much snow this spring.

Widespread Below Normal Temperatures

Average temperatures were unseasonably cool across a majority of the region yet again, with largest departures of 17°F to 21°F below normal in western Iowa and Minnesota (Figure 7). Portions of Ohio and Kentucky experienced near to above normal temperatures. Several daily temperature records were set, with the majority being record lows on April 19th and 20th.
 

April 17th and 18th Storm Event

Moist air surged ahead of a strong cold front and low-pressure system on April 17th and 18th, which brought heavy precipitation and damaging flash floods to portions of Iowa, Missouri, and Illinois (Figure 8). The first batch of rains on the 17th brought several inches of rainfall to northern Missouri, Iowa, and northern Illinois (Figure 9). Particularly hard hit was Chicago, Illinois metropolitan region (counties), where widespread rains of at least 4" resulted in several flash flood warnings across the region on the 17th (Figure 10). Some CoCoRaHS observers reported rainfall totals on the morning of the 18th of nearly 7" (Figure 11). The flash flooding in Chicago resulted in widespread road closures, including major interstates, school closures, numerous airport delays, and submerged streets and viaducts across the metropolitan region.

As the rains continued on the 18th, several more inches fell across the region, mainly in southern Illinois and Indiana (Figure 12). Widespread rain of at least 3" and in some cases 5" to 6" fell in central Indiana, which led to flooding of roads and high river levels.

As mentioned above, the significant rainfall associated with this event resulted in stream gauges across the affected areas reaching or exceeding flood levels and led to several inches of snowfall in the upper Midwest. In addition, large hail, high winds, and one tornado in Illinois were associated with this storm event (Figure 13). The largest hail of 2.75" was reported in Columbia, Missouri (Boone County) on the 17th and high winds of 90mph and 85mph were reported in Coatsburg and Loraine, Illinois (Adams County), respectively.

Drought Update

Luckily the rain and snowfall during the week brought some relief to the region in terms of drought. The latest release of the US Drought Monitor shows a reduction in the extent of extreme (D3), severe (D2), and moderate (D1) drought in Minnesota, Iowa, Missouri, and Wisconsin (Figure 14). Drought improvement is expected to continue in the western Midwest, according to the latest US Drought Outlook from the Climate Prediction Center (Figure 15).

Tough Spring for Farmers

As noted by a recent CoCoRaHS blog, this has been a tough spring for farmers in the Midwest. Unusual cold and wet weather is delaying planting and likely damaging some crops. In the Corn Belt states of Iowa, Illinois, and Indiana, little corn has been planted as of April 21st (1% in Illinois and Indiana, nothing in Iowa). The table below summarizes progress and comparison to the 5-year average in all nine Midwest states.

	% of Corn Planted (ending 4/21/13)	2008-2012 Average
Illinois	1%	24%
Indiana	1%	16%
Iowa	0%	14%
Kentucky	15%	32%
Michigan	0%	7%
Minnesota	0%	11%
Missouri	13%	29%
Ohio	1%	12%
Wisconsin	0%	4%

 

-MW-
The Minnesota State Climatology Office also contributed to this report.