Abstract
Excessive precipitation produced severe flooding in the
Mississippi River and Red River of the North Basins during
spring and summer 2011. The 2011 flooding was caused by
weather conditions that were affected in part by a La Niña
climate pattern. During the 2010–11 climatological winter
(December 2010–February 2011), several low pressure
troughs from the Rocky Mountains into the Ohio River subbasin
produced large amounts of precipitation. Precipitation
was above normal to record amounts in parts of the Missouri
River, Red River of the North, and upper Mississippi River
subbasins, and mostly normal to below normal in the Ohio
River and lower Mississippi River subbasins. During the 2011
climatological spring (March–May 2011), a large low pressure
trough over the continental States and a high pressure
ridge centered in the vicinity of the Gulf of Mexico combined
to produce storms with copious precipitation along frontal
boundaries across the Central States. Rain totals recorded
during the April 18–28, 2011, precipitation event were more
than 8 inches at several locations, while an impressive total of
16.15 inches was recorded at Cape Girardeau, Missouri. Several
locations in the Missouri River subbasin had rainfall totals
that were nearly one-third to one-half of their 1971–2000 normal
annual amounts during a May 16–31, 2011, precipitation
event. During June and July, thunderstorm development along
frontal boundaries resulted in areas of heavy rain across the
Missouri River, Red River of the North, and upper Mississippi
River subbasins, while rainfall in the lower Mississippi River
subbasin was mostly below normal.
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First posted March 11, 2013
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