March 15-21, 2010
Midwest Weekly Highlights - March 15-21, 2010
March Snow and Spring Flooding
Most of this week was relatively quiet across the region. A slow-moving storm brought heavy snow to portions of the region. In the upper Midwest, flooding continued along rivers and streams in Minnesota, including the Red River, in Iowa, and along the Mississippi River from the headwaters south through Missouri and Illinois.
There was a very large gradient in temperatures departures this week across the Midwest, with departures ranging from 6°F below normal in southwestern Missouri to 13°F above normal in northern Wisconsin (Figure 1). This pattern of colder than normal south and warmer than normal north has been persistent during the month of March. The warmer weather resulted in a significant reduction in snow cover across the Midwest this week. The only significant snow in the northern Midwest was located in far northern Minnesota and across the northern Michigan Upper Peninsula (Figure 2). A storm late in the week laid down a swath of snow from Missouri northeast into Michigan and that remained on the ground at the end of the period.
Precipitation across most of the region was well below normal this week (Figure 3). The exception was western Missouri, where precipitation was up to two times normal, and in southern Iowa and northwestern Illinois. This precipitation was associated with the late winter storm at the end of the week. There was little change in the status of drought in the Midwest on the March 16 U.S. Drought Monitor (Figure 4), although abnormal dryness had expanded into southern Indiana. Any effects from the precipitation with the late week storm will be reflected in the March 23 Drought Monitor.
Spring Snowstorm
High temperatures on March 19 were in the 60s across Missouri and the southeastern half of the region (Figure 5), and a number of record highs were set the last three days of the period. In keeping with March's changeable nature, the seasonably mild weather in place most of the week shifted to the east as a strong cold front sank southeast through the region on March 19 (Figure 6). A low pressure wave developing on the slow-moving front produced a swath of winter weather that extended from northern Texas into southern Michigan. On March 19 winter storm and heavy snow watches extended into western Missouri, and on March 20 much of the central Midwest was covered by a variety of winter weather advisories. The swath of snow in the Midwest extended from western Missouri across northern Illinois into southern lower Michigan (Figure 7). Snow was particularly heavy in southwestern Missouri, where 48 hour snowfall totals reached 13 inches in some locations, although most snowfall totals were in the 4 to 8 inch range (Figure 8). A number of locations from Missouri to Illinois set daily snowfall records on March 20-21, and four locations in Missouri set all-time daily snowfall records on March 21. Northeast winds blowing across Lake Michigan enhanced snowfall in northeastern Illinois, where amounts along the lake exceeded 5 inches (Figure 9). In many areas temperatures near freezing limited snow accumulations to non-pavement surfaces, so travel was not severely impacted. Travel conditions were most affected in western and southwestern Missouri where the snow was heavy and accompanied by strong northeast winds. There were numerous accidents on I-44 in Missouri, and there were four fatalities on other Missouri highways. As the storm shifted to the eastern half of the Midwest on March 21, sunshine and warmer weather was already melting the snow that had fallen.
Flooding Still a Threat
At the end of the week stream flows were still well above normal in the northern half of the region (Figure 10). Flooding in Minnesota resulted in many road closures, and there was localized flooding of some homes and outbuildings. Minnesota Governor Tim Pawlenty issued an executive order on March 17 declaring a state of emergency in Minnesota for a number of counties enabling disaster and flood-fighting assistance. The Red River at Fargo, ND crested at 36.99 feet on March 21, 19 feet above flood stage but a foot less than had been expected. A slow decline was expected barring any heavy precipitation.
Flooding was occurring along the Racoon River and Des Moines rivers in Iowa due to ice jams and runoff from melting snow. Fleur Drive, the main link between downtown Des Moines and the Des Moines Airport, was closed on March 16 owing to overflow from the Raccoon River. The Saylorville Reservoir, just upstream of Des Moines on the Des Moines River, has been rising about five feet per day for several days. Normal pool elevation is 836 feet but the lake is now up to 861 feet. The permanent spillway elevation is 884 feet but an inflatable bladder was installed a few years back to increase the spillway to 890 feet. The lake is expected, without additional precipitation, to crest very near 890 feet about March 26 or March 27 with outflow finally exceeding inflow around midday on March 27.
Along the Mississippi River, the city of Quincy, IL was planning to build a clay berm around the water treatment facility Monday to protect it against flooding. The city of Hannibal, MO was making plans to install at least two flood gates. The river stage at both Quincy and Hannibal was about 19 feet on March 21 and was expected to crest around 20 feet within a day or two before beginning a slow decline.
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