General Weather Conditions and Precipitation Contributing 

to the 2011 Flooding in the Mississippi River and Red River of 

the North Basins, December 2010 through July 2011

Chapter B of

2011 Floods of the Central United States

Professional Paper 1798–B

U.S. Department of the Interior

U.S. Geological Survey
Front cover. Left: U.S. Geological Survey (USGS) hydrographer Stacey Kinsey measuring discharge on the Musselshell River, Montana, 

May 27, 2011. Photograph by Tim Morgan, USGS.

Right: Megan VanDenHeuvel (Journeyman Forecaster), Scott Coulston (Journeyman Forecaster), and Gina Loss (Senior 

Service Hydrologist), National Weather Service (NWS) Great Falls Weather Forecast Office, measuring snow water 

equivalent in northern Blaine County, Montana, March 7, 2011. Photograph by Ben Schott (Warning Coordination 

 Meteorologist).

Background: View of flooding from Nebraska City, Nebraska, looking east across the Missouri River, August 2, 2011. 

Photograph by Robert Swanson, USGS.

Back cover. Goose Lake in Custer National Forest, Beartooth Mountains, Montana, looking north, July 3, 2011. Photograph by 

David Filcher, geologist (retired).
General Weather Conditions and 

Precipitation Contributing to the 2011 

Flooding in the Mississippi River and Red 

River of the North Basins, December 2010 

through July 2011

By Kevin C. Vining, Katherine J. Chase, and Gina R. Loss

Professional Paper 1798–B

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS.

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Vining, K.C., Chase, K.J., and Loss, G.R., 2013, General weather conditions and precipitation contributing to the 2011 

flooding in the Mississippi River and Red River of the North Basins, December 2010 through July 2011: U.S. Geological Survey Professional Paper 1798–B, 22 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

General Weather Conditions........................................................................................................................3

Precipitation Patterns ...................................................................................................................................4

Precipitation on the Mississippi River Basin ............................................................................................5

Lower Mississippi River Subbasin...................................................................................................12

Ohio River Subbasin ...........................................................................................................................13

Missouri River Subbasin....................................................................................................................16

Upper Mississippi River Subbasin ...................................................................................................18

Precipitation on the Red River of the North Basin .................................................................................20

Summary........................................................................................................................................................20

References Cited..........................................................................................................................................21

Figures

1. Map showing locations of subbasins and weather stations within the Mississippi

River Basin and the Red River of the North Basin ..................................................................2

2. Map showing climate-division precipitation ranks for climatological winter 2010–11

(December 2010–February 2011) based on about 116 years of record................................4

3. Map showing climate-division precipitation ranks for climatological spring 2011

(March–May 2011) based on about 116 years of record .......................................................5

4. Map showing December 2010 observed precipitation...........................................................6

5. Map showing January 2011 observed precipitation...............................................................6

6. Map showing February 2011 observed precipitation .............................................................7

7. Map showing March 2011 observed precipitation .................................................................7

8. Map showing April 2011 observed precipitation.....................................................................8

9. Map showing May 2011 observed precipitation .....................................................................8

10. Map showing June 2011 observed precipitation ....................................................................9

11. Map showing July 2011 observed precipitation......................................................................9

12. Map showing approximate position of primary weather features that contributed 

to the April 18–28, 2011, precipitation event in the Ohio River subbasin...........................14

13. Graphs showing precipitation totals during the April 18–28, 2011, precipitation

event, total precipitation for April 2011, and the 1971–2000 normal April

precipitation for five locations in or near the Ohio River subbasin....................................15

14. Map showing approximate position of primary weather features that contributed 

to the May 16–31, 2011, rainfall event in the Missouri River subbasin..............................17

15. Graphs showing precipitation totals during the May 16–31, 2011, precipitation

event, precipitation totals for May 2011, and the 1971–2000 normal May

precipitation for six locations in the Missouri River subbasin............................................19
iv

Tables

1. Summary of monthly precipitation totals for December 2010 through July 20111 

and normals for 1971–20002 for selected States in the Mississippi and Red River 

of the North Basins.....................................................................................................................10

2. Summary of monthly precipitation totals for December 2010 through July 20111 

and normals for 1971—20002 for selected weather stations in the Mississippi 

River Basin...................................................................................................................................11

3. Summary of precipitation totals during the April 18–28, 2011, precipitation event,

total precipitation for April 2011, the 1971–2000 normal April precipitation, and

the 30-year average annual precipitation (1971–2000)for selected weather

stations in and near the Ohio River subbasin ........................................................................14

4. Summary of precipitation totals during the May 16–31, 2011, precipitation event,

total precipitation for May 2011, the 1971–2000 normal May precipitation, and 

the 30-year average annual precipitation (1971–2000)for selected weather 

stations in the Missouri River subbasin..................................................................................18

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

acre-foot (acre-ft) 1,233 cubic meter (m3)

acre-foot (acre-ft) 0.001233 cubic hectometer (hm3)

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).
General Weather Conditions and Precipitation 

Contributing to the 2011 Flooding in the Mississippi River 

and Red River of the North Basins, December 2010 through 

July 2011

By Kevin C. Vining,1 Katherine J. Chase,1 and Gina R. Loss2

1

U.S. Geological Survey.

2

U.S. Department of Commerce, National Oceanic and 

Atmospheric Administration, National Weather Service.

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.

Introduction

Excessive precipitation produced severe flooding in the 

Mississippi River and Red River of the North Basins during 

spring and summer 2011. This report, one of a series of reports 

that documents the 2011 flooding in the Central United States, 

describes the weather conditions and precipitation in the Mississippi River and the Red River of the North Basins during 

climatological winter of 2010–11 (December 2010–February 

2011), climatological spring of 2011 (March–May 2011), and 

early climatological summer of 2011 (June–July 2011). 

The Mississippi River and Red River of the North Basins 

encompass about 41 percent of the conterminous United States 

(U.S. Army Corps of Engineers, 2012b) (fig. 1). The Mississippi River Basin extends from the Rocky Mountains and 

semi-arid prairies of Montana and Wyoming to the temperate 

humid areas near the Great Lakes to the subtropical lowlands 

near the Gulf of Mexico. The Red River of the North Basin 

lies in the humid continental prairies of Minnesota, North 

Dakota, and South Dakota (Critchfield, 1974). These differences in climate are indicative of the incongruity of precipitation each of these regions receives each year on average or at 

any particular time; the lower Mississippi River subbasin may 

have torrential rainfall from tropical systems at the same time 

that the Northern Plains face drought. Conversely, as was the 

case during December 2010–July 2011, the lower Mississippi 

River subbasin may have drought even though precipitation 

is above normal in the Northern Plains States. Conditions 

may also occur such that several regions receive significant 

precipitation concurrently or in a sequential pattern that results 

in widespread significant flooding across portions of the 

United States.

The USGS Souris River at Foxholm, North Dakota streamgage is half inundated by water about 

30 miles northwest of Minot, June 2011. Photograph by Marisa Lubeck, U.S. Geological Survey.
Lake Superior Lake MichiganLake Huron Lake Erie 

Red

River

River

Wisconsin

River

River

GULF

OF

MEXIC

O

Platte

River

Missouri

River

Arkansas

Canadian

MississippiMississippi

River

River

Tennessee

Illinois

River

Rainy

River

River

MissouriMissouri

Red River of the North

PACIFIC OCEAN

YellowstoneYellowstone

River

Ohio

River

River

Souris

MONTANA

WYOMING

SASKATCHEWAN

North

Fort PeckReservoir

GARRISON DAM

EXPLANATION

Mississippi River Basin

Ohio River subbasinUpper Mississippi River subbasinLower Mississippi River subbasinMissouri River subbasin

Red River of the North BasinWeather station

Base from Esri digital data, 2000, 1:3,000,000

Albers Equal-area Conic projectionStandard parallels 20°N and 60°N, central meridian 96°W

North American Datum of 1983 (NAD 83)

Watershe

Cincinnati

Memphis

Regina

CANADA

UNITED STATES

MEXICO

Minot

Omaha

Fargo

Madison

Glasgow Williston

Louisville

MilesCity

Evansville

Minneapolis

TerreHaute

BatonRouge

GrandForks

GreatFalls

Oklahoma

City

Cape Girardeau

Rapid City

Billings Bismarck

Springfield

NORTH DAKOTA

SOUTH DAKOTA

MINNESOTA

120°

110° 100°

80°

40°

30°

90°

130°

0 200 400 600 MILES

0 200 400 600 KILOMETERS

Chanhassen

Rocky MountainsRocky Mountains Lake Sakakawea Aberdeen

Figure 1. Locations of subbasins and weather stations within the Mississippi River Basin and the Red River of the North Basin.
General Weather Conditions 3

Precipitation and the causative weather events are 

described for subbasins of the Mississippi River and Red 

River of the North Basins as defined in the report. The lower 

Mississippi River subbasin includes the areas of the Mississippi River and tributaries downstream from the confluence 

with the Ohio River. The Missouri River subbasin includes 

the areas of the Missouri River and tributaries. The upper 

Mississippi River subbasin includes the areas of the Mississippi River and the tributaries upstream from the confluence 

with the Ohio River but does not include the Ohio River or 

Missouri River subbasins. The Red River of the North Basin 

includes the areas of the Red River of the North and tributaries 

including the Souris River within the United States.

Preparation of this report required the cooperation of 

persons in several organizations. The authors are particularly 

appreciative of the cooperation of personnel at the National 

Oceanic and Atmospheric Administration’s (NOAA) National 

Weather Service (NWS) for providing data, written materials, 

and reviews of the report.

Unless otherwise specified, all climate data presented 

were obtained from the NOAA National Climate Data Center 

Web sites concerning the state of the climate (National Oceanic and Atmospheric Administration, 2011a). Descriptions of 

meteorological phenomena are from the Hydrometeorological Prediction Center (2012) and from the National Weather 

Service Performance Management Homepage (National 

Oceanic and Atmospheric Administration, 2012a). Climate 

normals presented are for the period 1971–2000, because the 

1981–2010 normals had not been published when the data for 

this report were obtained. (The average precipitation for any 

given 30-year period is termed the “normal” precipitation for 

the given period.)

General Weather Conditions

The 2011 flooding in the Mississippi River and Red 

River of the North Basins resulted from weather conditions 

during December 2010 through July 2011 that were affected 

in part by a La Niña climate pattern (National Oceanic and 

Atmospheric Administration, 2011a). The La Niña pattern is 

characterized by cooler-than-average sea surface temperatures 

in the central and east-central equatorial Pacific Ocean and a 

strong high pressure area in the northern Pacific Ocean region. 

Also during a La Niña, an area of high pressure exists over 

the south and southeastern regions of the United States. As a 

result, the northern jet stream can be positioned to bring cooler 

polar air into the western and northern United States while 

a southern jet stream brings Pacific moisture into the Rocky 

Mountain region and the Mississippi River and Red River of 

the North Basins. The La Niña pattern tends to produce cooler 

and wetter than normal weather conditions over the western 

and north-central regions of the Mississippi River and Red 

River of the North Basins and often warmer and drier than 

normal weather conditions over the southern Mississippi River 

Basin. The La Niña pattern developed during mid-2010 and 

continued well into 2011. 

Before the onset of La Niña during climatological winter 

2010–11, a news release by NOAA’s Climate Prediction Center on October 21, 2010, provided a summary of the potential 

effects of La Niña on the upcoming winter (National Oceanic 

and Atmospheric Administration, 2010):

The Pacific Northwest should brace for a colder and 

wetter than average winter, while most of the South 

and Southeast will be warmer and drier than average through February 2011, according to the annual 

Winter Outlook released today by NOAA’s Climate 

Prediction Center. A moderate to strong La Niña will 

be the dominant climate factor influencing weather 

across most of the United States this winter. 

From the same NOAA news release, the Climate Prediction 

Center indicated:

La Niña is in place and will strengthen and persist 

through the winter months, providing a better understanding of what to expect between December and 

February. This is a good time for people to review 

the outlook and begin preparing for what winter may 

have in store. 

Regional highlights quoted from the news release described 

potential effects of La Niña on winter and early spring conditions in parts of the Mississippi River and Red River of the 

North Basins:

• Pacific Northwest: colder and wetter than average. 

La Niña often brings lower than average temperatures 

and increased mountain snow to the Pacific Northwest 

and western Montana during the winter months, which 

is good for the replenishment of water resources and 

winter recreation but can also lead to greater flooding 

and avalanche concerns.

• Northern Plains: colder and wetter than average. 

Likely to see increased storminess and flooding.

• Ohio and Tennessee Valleys: warmer and wetter than 

average. Likely to see increased storminess and flooding. 

• Southern Plains, Gulf Coast States, and Southeast: 

warmer and drier than average. This will likely exacerbate drought conditions in these areas. 
4 Precipitation Contributing to the 2011 Flooding in the Mississippi River and Red River of the North Basins

Precipitation Patterns

The La Niña and its associated weather conditions 

persisted through climatological winter 2010–11 and climatological spring 2011. Climatological winter 2010–11 was quite 

active with storms passing through the northern portion of the 

United States. All the climate divisions in South Dakota had 

much above normal winter precipitation, and the northeast 

climate division in Montana had a record wet winter (National 

Oceanic and Atmospheric Administration, 2011a) (fig. 2). 

Conversely, the South-Central and areas of the Southeastern 

United States, especially the lower Mississippi River subbasin, had conditions that were much drier than normal. During 

climatological spring 2011, much of the northern two-thirds 

of the Mississippi River Basin continued to have wetter than 

normal conditions, while the Southern Plains and the lower 

Mississippi River Basin in Louisiana continued to have much 

drier than normal conditions, with record dryness observed 

over much of Texas, Oklahoma, and New Mexico (National 

Oceanic and Atmospheric Administration, 2011a) (fig. 3). 

Precipitation patterns across the Red River of the North 

and Mississippi River Basins from December 2010 through 

July 2011 followed the mean position of the jet stream 

(National Oceanic and Atmospheric Administration, 2011b). 

During December, January, and February, a southward push 

of the jet stream steered several low pressure troughs across 

the country from the Rocky Mountains into the Ohio River 

subbasin producing large amounts of precipitation (figs. 4–6). 

As some low pressure systems would develop deep into the 

southern portions of the United States, they would create a 

split in the storm track. Low pressure troughs that followed 

the southern branch of the storm track brought substantial 

precipitation to the Lower Mississippi River subbasin in 

January (fig. 5) and also to the Ohio River subbasin in February (fig. 6). From March through May, a large low pressure 

trough dominated the continental States, and a high pressure 

ridge was centered in the vicinity of the Gulf of Mexico. This 

weather combination produced storms with copious precipitation along frontal boundaries that were steered across the 

Central States before moving to the northeast into the Ohio 

River subbasin (figs. 7–9). The geographical tracking of these 

storms brought precipitation into the Missouri River subbasin 

as well. During June and July, moisture from the southwestern monsoon and the Gulf of Mexico worked its way into the 

Plains States. Low pressure troughs moving across the country 

interacted with this moist unstable air; thunderstorm development along frontal boundaries resulted in areas of heavy rain 

across the Northern Plains States into the Missouri and upper 

Mississippi River subbasins (figs. 10 and 11). Excessive precipitation that fell on already saturated ground and ran off into 

already full streams and rivers produced severe flooding in the 

Mississippi River and Red River of the North Basins during 

spring and summer 2011 (Minnesota Climatology Working 

Group, 2011). Meanwhile, the high pressure ridge that had 

built over the Southern Plains kept that area mostly dry.

Record wettest

Much above normal

Above normal

Near normal

Below normal

Much below normal

Record driest

Precipitation rank

Basin or subbasin boundary

EXPLANATION

Ohio 

River

subbasin

Red River of the North Basin

Upper Mississippi

River subbasin

Lower Mississippi

River subbasin

0 200 400 600 MILES

0 400200 600 KILOMETERS

120°

110° 100° 80°

40°

30°

90° 70°

Missouri River subbasin

Figure 2. Climate-division precipitation ranks for climatological winter 2010–11 (December 2010–February 2011) based on about 

116 years of record.
Precipitation on the Mississippi River Basin 5

Precipitation on the Mississippi River 

Basin

Climatological winter 2010–11 was characterized by the 

passage of several deep low pressure troughs, each of which 

allowed for the infiltration of cold, continental polar air. The 

combination of moisture associated with these troughs and 

cold air set the stage for significant snowfall across the Rockies and northern portion of the Mississippi River Basin. At the 

end of December 2010, Montana, Wyoming, North Dakota, 

South Dakota, Minnesota, Colorado, and most of Nebraska 

were covered with snow (National Oceanic and Atmospheric 

Administration, 2011c). By the end of February, the snow 

water equivalent (SWE) in the mountains was near to a little 

above average; southwestern Montana had approximately 

17 inches SWE, the plains on the eastern side of the Rocky 

Mountains approximately 20 inches SWE, central Montana 

mountains approximately 18 inches SWE, and the mountains 

of Montana and Wyoming, which contain headwaters of the 

Yellowstone River, approximately 12 inches of SWE. On the 

plains of eastern Montana, North Dakota, and South Dakota, 

the series of snowstorms created a widespread, deep snowpack 

with some areas receiving nearly three times their average 

annual snowfall. At the end of the climatological winter, SWE 

over the plains ranged from 4 to 12 inches. South Dakota 

and Montana recorded their fourth and ninth wettest winter 

periods, respectively (National Oceanic and Atmospheric 

Administration, 2012b).

The weather pattern that dominated during climatological 

winter 2010–11 continued through climatological spring 2011 

(National Oceanic and Atmospheric Administration, 2011a). 

Texas recorded its driest spring on record, with statewideaveraged precipitation of only 2.66 inches (table 1), almost 

5 inches below normal. Nearby, Louisiana had its sixth driest 

spring on record while Arkansas had its tenth-wettest spring 

on record. As the jet stream continued to flow over the Northern United States, several low pressure troughs were steered 

along its path. Frequent storm systems continued to bring 

precipitation to the northern Rocky Mountains and Northern 

Plains. Storm systems also developed in the mid-Mississippi 

Valley and moved northeastward across the Ohio Valley 

region. The divisional ranks of precipitation for spring (fig. 3) 

show that southern Missouri and northern Arkansas into the 

Ohio River subbasin and many locations in the Missouri River 

subbasin recorded above normal precipitation. Above-normal 

spring precipitation fell in the Ohio River subbasin during 

late April and in the Missouri River subbasin during late May 

(National Oceanic and Atmospheric Administration, 2011a). 

Details about these precipitation events are discussed in the 

sections about each subbasin. Monthly precipitation totals 

for December 2010 through July 2011 for selected weather 

stations across the Mississippi River Basin are presented in 

table 2.

Record wettest

Much above normal

Above normal

Near normal

Below normal

Much below normal

Record driest

Precipitation rank

Basin or subbasin boundary

EXPLANATION

Ohio 

River

subbasin

Missouri River subbasin

Red River of the North Basin

Upper Mississippi

River subbasin

Lower Mississippi

River subbasin

0 200 400 600 MILES

0 400200 600 KILOMETERS

120°

110° 100° 80°

40°

30°

90° 70°

Figure 3. Climate-division precipitation ranks for climatological spring 2011 (March–May 2011) based on about 116 years of 

record.
6 Precipitation Contributing to the 2011 Flooding in the Mississippi River and Red River of the North Basins

Ohio River

subbasin

Red River of the North Basin

Upper Mississippi River

subbasin

Lower Mississippi River

subbasin

Missouri River

subbasin

EXPLANATION

Base from National Oceanic and Atmospheric Administration, 2011b Precipitation data from National Oceanic and Atmospheric 

Administration, 2011b; Basin boundaries from Watermolen, 2005

Ohio River

subbasin

Red River of the North Basin

Upper Mississippi River

subbasin

Lower Mississippi River

subbasin

Missouri River

subbasin

EXPLANATION

Precipitation, in 

inches

Basin or subbasin 

boundary

Greater than 20

15 to 20

10 to 15

8 to 10

6 to 8

5 to 6

4 to 5

3 to 4

2 to 3

1.5 to 2

1 to 1.5

0.5 to 1

0.25 to 0.5

0.1 to 0.25

0.1

Rocky

Mountains

Rocky

Mountains

0 200 400 600 MILES

0 400200 600 KILOMETERS

120°

110° 100° 90° 80°

70°

40°

30°

60°

50°

Figure 4. December 2010 observed precipitation.

0 200 400 600 MILES

0 400200 600 KILOMETERS

120°

110° 100° 90° 80°

70°

40°

30°

60°

50°

Ohio River

subbasin

Red River of the North Basin

Upper Mississippi River

subbasin

Lower Mississippi River

subbasin

Missouri River

subbasin

Ohio River

subbasin

Red River of the North Basin

Upper Mississippi River

subbasin

Lower Mississippi River

subbasin

Missouri River

subbasin

Rocky

Mountains

Rocky

Mountains

EXPLANATION

Precipitation, in 

inches

Basin or subbasin 

boundary

Greater than 20

15 to 20

10 to 15

8 to 10

6 to 8

5 to 6

4 to 5

3 to 4

2 to 3

1.5 to 2

1 to 1.5

0.5 to 1

0.25 to 0.5

0.1 to 0.25

0.1

Base from National Oceanic and Atmospheric Administration, 2011b Precipitation data from National Oceanic and Atmospheric 

Administration, 2011b; Basin boundaries from Watermolen, 2005

Figure 5. January 2011 observed precipitation.
Precipitation on the Mississippi River Basin 7

0 200 400 600 MILES

0 400200 600 KILOMETERS

120°

110° 100° 90° 80°

70°

40°

30°

60°

50°

Ohio River

subbasin

Red River of the North Basin

Upper Mississippi River

subbasin

Lower Mississippi River

subbasin

Missouri River

subbasin

Ohio River

subbasin

Red River of the North Basin

Upper Mississippi River

subbasin

Lower Mississippi River

subbasin

Missouri River

subbasin

Rocky

Mountains

Rocky

Mountains

EXPLANATION

Precipitation, in 

inches

Basin or subbasin 

boundary

Greater than 20

15 to 20

10 to 15

8 to 10

6 to 8

5 to 6

4 to 5

3 to 4

2 to 3

1.5 to 2

1 to 1.5

0.5 to 1

0.25 to 0.5

0.1 to 0.25

0.1

Base from National Oceanic and Atmospheric Administration, 2011b Precipitation data from National Oceanic and Atmospheric 

Administration, 2011b; Basin boundaries from Watermolen, 2005

Figure 6. February 2011 observed precipitation.

0 200 400 600 MILES

0 400200 600 KILOMETERS

120°

110° 100° 90° 80°

70°

40°

30°

60°

50°

Ohio River

subbasin

Red River of the North Basin

Upper Mississippi River

subbasin

Lower Mississippi River

subbasin

Missouri River

subbasin

Ohio River

subbasin

Red River of the North Basin

Upper Mississippi River

subbasin

Lower Mississippi River

subbasin

Missouri River

subbasin

Rocky

Mountains

Rocky

Mountains

EXPLANATION

Precipitation, in 

inches

Basin or subbasin 

boundary

Greater than 20

15 to 20

10 to 15

8 to 10

6 to 8

5 to 6

4 to 5

3 to 4

2 to 3

1.5 to 2

1 to 1.5

0.5 to 1

0.25 to 0.5

0.1 to 0.25

0.1

Base from National Oceanic and Atmospheric Administration, 2011b Precipitation data from National Oceanic and Atmospheric 

Administration, 2011b; Basin boundaries from Watermolen, 2005

Figure 7. March 2011 observed precipitation.
8 Precipitation Contributing to the 2011 Flooding in the Mississippi River and Red River of the North Basins

0 200 400 600 MILES

0 400200 600 KILOMETERS

120°

110° 100° 90° 80°

70°

40°

30°

60°

50°

Ohio River

subbasin

Red River of the North Basin

Upper Mississippi River

subbasin

Lower Mississippi River

subbasin

Missouri River

subbasin

Base from National Oceanic and Atmospheric Administration, 2011b

Ohio River

subbasin

Red River of the North Basin

Upper Mississippi River

subbasin

Lower Mississippi River

subbasin

Missouri River

subbasin

Rocky

Mountains

Rocky

Mountains

EXPLANATION

Precipitation, in 

inches

Basin or subbasin 

boundary

Greater than 20

15 to 20

10 to 15

8 to 10

6 to 8

5 to 6

4 to 5

3 to 4

2 to 3

1.5 to 2

1 to 1.5

0.5 to 1

0.25 to 0.5

0.1 to 0.25

0.1

Precipitation data from National Oceanic and Atmospheric 

Administration, 2011b; Basin boundaries from Watermolen, 2005

Figure 8. April 2011 observed precipitation.

0 200 400 600 MILES

0 400200 600 KILOMETERS

120°

110° 100° 90° 80°

70°

40°

30°

60°

50°

Ohio River

subbasin

Red River of the North Basin

Upper Mississippi River

subbasin

Lower Mississippi River

subbasin

Missouri River

subbasin

Base from National Oceanic and Atmospheric Administration, 2011b Precipitation data from National Oceanic and Atmospheric 

Administration, 2011b; Basin boundaries from Watermolen, 2005

Ohio River

subbasin

Red River of the North Basin

Upper Mississippi River

subbasin

Lower Mississippi River

subbasin

Missouri River

subbasin

Rocky

Mountains

Rocky

Mountains

EXPLANATION

Precipitation, in 

inches

Basin or subbasin 

boundary

Greater than 20

15 to 20

10 to 15

8 to 10

6 to 8

5 to 6

4 to 5

3 to 4

2 to 3

1.5 to 2

1 to 1.5

0.5 to 1

0.25 to 0.5

0.1 to 0.25

0.1

Figure 9. May 2011 observed precipitation.
Precipitation on the Mississippi River Basin 9

0 200 400 600 MILES

0 400200 600 KILOMETERS

120°

110° 100° 90° 80°

70°

40°

30°

60°

50°

Ohio River

subbasin

Red River of the North Basin

Upper Mississippi River

subbasin

Lower Mississippi River

subbasin

Missouri River

subbasin

Ohio River

subbasin

Red River of the North Basin

Upper Mississippi River

subbasin

Lower Mississippi River

subbasin

Missouri River

subbasin

0.1

Rocky

Mountains

Rocky

Mountains

EXPLANATION

Precipitation, in 

inches

Basin or subbasin 

boundary

Greater than 20

15 to 20

10 to 15

8 to 10

6 to 8

5 to 6

4 to 5

3 to 4

2 to 3

1.5 to 2

1 to 1.5

0.5 to 1

0.25 to 0.5

0.1 to 0.25

0.1

Base from National Oceanic and Atmospheric Administration, 2011b Precipitation data from National Oceanic and Atmospheric 

Administration, 2011b; Basin boundaries from Watermolen, 2005

Figure 10. June 2011 observed precipitation.

Ohio River

subbasin

Red River of the North Basin

Upper Mississippi River

subbasin

Lower Mississippi River

subbasin

Missouri River

subbasin

Ohio River

subbasin

Red River of the North Basin

Upper Mississippi River

subbasin

Lower Mississippi River

subbasin

Missouri River

subbasin

Rocky

Mountains

Rocky

Mountains

EXPLANATION

Precipitation, in 

inches

Basin or subbasin 

boundary

Greater than 20

15 to 20

10 to 15

8 to 10

6 to 8

5 to 6

4 to 5

3 to 4

2 to 3

1.5 to 2

1 to 1.5

0.5 to 1

0.25 to 0.5

0.1 to 0.25

0.1

Base from National Oceanic and Atmospheric Administration, 2011b

120°

110° 100° 90° 80°

70°

40°

30°

60°

50°

0 200 400 600 MILES

0 400200 600 KILOMETERS

Precipitation data from National Oceanic and Atmospheric 

Administration, 2011b; Basin boundaries from Watermolen, 2005

Figure 11. July 2011 observed precipitation.
10 Precipitation Contributing to the 2011 Flooding in the Mississippi River and Red River of the North Basins

Table 1. Summary of monthly precipitation totals for December 2010 through July 20111 and normals for 1971–20002 for selected States 

in the Mississippi and Red River of the North Basins.

State Total monthly precipitation, in inches

December January February March April May June July

Arkansas December 2010—July 2011 1.48 1.55 4.17 2.74 10.41 8.45 1.62 2.10

1971—2010 Normals 4.68 3.65 3.61 4.93 4.82 5.20 4.31 3.52

Colorado December 2010—July 2011 1.11 0.52 0.85 0.84 1.66 2.14 0.87 2.61

1971—2010 Normals 0.76 0.79 0.75 1.29 1.47 1.92 1.44 2.01

Illinois December 2010—July 2011 1.82 1.19 3.17 2.67 7.40 5.18 6.46 3.77

1971—2010 Normals 2.73 1.97 1.99 3.22 3.83 4.31 4.12 3.94

Indiana December 2010—July 2011 1.52 1.55 4.17 3.46 9.42 6.47 5.12 2.91

1971—2010 Normals 3.07 2.44 2.31 3.40 3.96 4.47 4.25 4.19

Iowa December 2010—July 2011 1.29 0.92 1.42 1.52 3.78 4.87 6.30 3.44

1971—2010 Normals 1.23 0.95 0.98 2.20 3.33 4.23 4.62 4.26

Kansas December 2010—July 2011 0.20 0.44 1.13 1.13 1.83 3.42 2.80 2.62

1971—2010 Normals 0.96 0.77 0.91 2.25 2.58 4.18 3.88 3.61

Kentucky December 2010—July 2011 3.08 2.04 4.72 5.24 11.74 6.70 5.26 3.96

1971—2010 Normals 4.38 3.77 3.76 4.60 4.19 5.05 4.34 4.47

Louisiana December 2010—July 2011 1.94 4.66 2.08 3.73 2.62 1.51 3.25 6.39

1971—2010 Normals 5.42 5.91 4.66 5.32 4.89 5.46 5.20 5.15

Minnesota December 2010—July 2011 1.88 1.05 0.67 1.32 2.69 4.10 4.39 4.93

1971—2010 Normals 0.77 0.86 0.64 1.45 2.06 3.06 4.05 3.95

Mississippi December 2010—July 2011 1.55 4.39 2.50 6.60 6.20 1.94 3.21 5.75

1971—2010 Normals 5.50 5.92 4.96 6.30 5.61 5.40 4.47 4.80

Missouri December 2010—July 2011 0.89 1.08 3.48 3.51 7.45 6.14 4.23 2.43

1971—2010 Normals 2.79 1.95 2.15 3.51 4.04 4.82 4.26 3.95

Montana December 2010—July 2011 1.11 1.10 0.94 1.07 1.82 5.24 3.03 1.27

1971—2010 Normals 0.78 0.80 0.60 0.90 1.30 2.34 2.40 1.65

Nebraska December 2010—July 2011 0.39 0.91 0.62 0.89 2.78 5.31 3.97 3.67

1971—2010 Normals 0.56 0.51 0.60 1.66 2.38 3.75 3.45 3.27

North Dakota December 2010—July 2011 1.23 0.90 0.34 1.05 1.75 3.89 3.83 3.93

1971—2010 Normals 0.43 0.50 0.45 0.80 1.40 2.31 3.19 2.75

Ohio December 2010—July 2011 2.07 1.55 4.50 4.24 7.70 6.40 3.71 3.72

1971—2010 Normals 2.91 2.51 2.27 3.06 3.47 4.06 4.10 4.09

Oklahoma December 2010—July 2011 0.87 0.35 1.46 0.71 3.33 4.07 1.13 0.71

1971—2010 Normals 2.04 1.48 1.78 3.07 3.32 5.13 4.24 2.73

Pennsylvania December 2010—July 2011 3.50 1.86 3.60 5.65 7.80 5.68 3.00 2.81

1971—2010 Normals 3.11 3.04 2.58 3.41 3.55 4.07 4.45 4.15

South Dakota December 2010—July 2011 0.98 0.90 1.10 1.00 2.24 4.50 4.67 3.37

1971—2010 Normals 0.43 0.45 0.53 1.30 2.11 3.10 3.23 2.75

Tennessee December 2010—July 2011 2.91 3.16 4.11 6.86 9.62 5.09 5.71 3.32

1971—2010 Normals 5.17 4.66 4.31 5.60 4.51 5.33 4.48 4.67

Texas December 2010—July 2011 0.74 1.63 0.74 0.29 0.77 1.60 1.03 0.73

1971—2010 Normals 1.85 1.59 1.67 1.85 2.14 3.52 3.35 2.22

West Virginia December 2010—July 2011 3.44 2.13 2.88 5.69 7.51 5.08 3.99 3.71

1971—2010 Normals 3.38 3.46 3.11 3.97 3.63 4.57 4.23 4.75

Wisconson December 2010—July 2011 1.87 0.91 1.13 2.39 3.69 2.95 4.27 4.45

1971—2010 Normals 1.34 1.22 1.00 1.96 2.86 3.37 4.02 4.07

Wyoming December 2010—July 2011 1.09 0.60 0.69 0.86 1.72 4.11 1.38 1.00

1971—2010 Normals 0.59 0.63 0.57 0.86 1.36 2.06 1.58 1.33

1

National Oceanic and Atmospheric Administration, 2012c.

2

National Oceanic and Atmospheric Administration, 2002.
Precipitation on the Mississippi River Basin 11

Table 2. Summary of monthly precipitation totals for December 2010 through July 20111 and normals for 1971—20002 for selected 

weather stations in the Mississippi River Basin.

Station Total monthly precipitation, in inches

December January February March April May June July

Lower Mississippi River subbasin

Baton Rouge, Louisiana December 2010—July 2011 4.59 5.28 1.90 6.93 0.99 0.59 4.74 6.22

1971—2000 Normals 5.26 6.19 5.10 5.07 5.56 5.34 5.33 5.96

Memphis, Tennessee December 2010—July 2011 2.91 2.13 3.53 4.65 12.58 7.86 3.53 3.09

1971—2000 Normals 5.48 3.92 4.39 5.18 5.36 4.97 4.36 4.64

Oklahoma City, Oklahoma December 2010—July 2011 0.13 0.10 2.09 0.03 0.99 9.21 1.24 3.04

1971—2000 Normals 1.89 1.28 1.56 2.90 3.00 5.44 4.63 2.94

Ohio River subbasin

Cincinnati, Ohio/Covington 

Airport, Kentucky

December 2010—July 2011 1.77 1.58 5.79 4.55 13.52 6.71 8.89 2.22

1971—2000 Normals 3.28 2.92 2.75 3.90 3.96 4.59 4.42 3.75

Louisville, Kentucky December 2010—July 2011 1.66 1.48 5.69 5.17 13.97 7.81 7.14 2.35

1971—2000 Normals 3.69 3.28 3.25 4.41 3.91 4.88 3.76 4.30

Terre Haute, Indiana December 2010—July 2011 1.74 0.61 3.88 2.94 11.01 5.33 4.62 2.62

1971—2000 Normals 3.01 2.13 2.58 3.68 4.12 4.46 4.09 4.45

Missouri River subbasin

Great Falls, Montana December 2010—July 2011 1.56 0.46 1.77 0.42 2.83 4.12 2.58 0.87

1971—2000 Normals 0.67 0.68 0.51 1.01 1.40 2.53 2.24 1.45

Rapid City, South Dakota December 2010—July 2011 0.57 0.36 1.16 0.85 2.13 8.24 4.70 1.16

1971—2000 Normals 0.40 0.37 0.46 1.03 1.86 2.96 2.83 2.03

Williston, North Dakota December 2010—July 2011 1.95 1.30 0.55 0.98 2.99 5.28 1.86 2.34

1971—2000 Normals 0.57 0.54 0.39 0.74 1.05 1.88 2.36 2.28

Upper Mississippi River subbasin

Chanhassen, Minnesota December 2010—July 2011 2.90 0.98 1.14 2.32 3.02 4.78 3.98 5.38

1971—2000 Normals 0.84 0.93 0.62 1.77 2.40 3.65 4.21 4.43

Madison, Wisconsin December 2010—July 2011 1.49 1.28 1.59 2.96 3.61 2.40 3.55 1.85

1971—2000 Normals 1.66 1.25 1.28 2.28 3.35 3.25 4.05 3.93

Springfield, Illinois December 2010—July 2011 1.67 0.95 2.81 1.67 5.46 3.35 6.31 1.08

1971—2000 Normals 2.54 1.62 1.80 3.15 3.36 4.06 3.77 3.53

Red River of the North subbasin

Fargo, North Dakota December 2010—July 2011 1.75 0.90 0.08 1.84 2.02 4.30 4.41 4.35

1971—2000 Normals 0.57 0.76 0.59 1.17 1.37 2.61 3.51 2.88

Grand Forks, North Dakota December 2010—July 2011 0.72 0.85 0.04 0.76 2.40 2.45 3.34 2.69

1971—2000 Normals 0.55 0.68 0.58 0.89 1.23 2.21 3.03 3.06

Minot, North Dakota December 2010—July 2011 0.73 0.42 0.06 0.79 1.34 6.22 2.97 5.58

1971—2000 Normals 0.63 0.65 0.53 1.05 1.55 2.31 3.15 2.70

1

National Oceanic and Atmospheric Administration (2011d).

2

National Oceanic and Atmospheric Administration (2012d).
12 Precipitation Contributing to the 2011 Flooding in the Mississippi River and Red River of the North Basins

Lower Mississippi River Subbasin

As most weather systems were being steered across the 

northern portion of the United States during the climatological 

winter of 2010–11, the lower Mississippi River subbasin had 

mostly dry conditions (fig. 2). Climatological spring brought 

a slight shift in the weather pattern with passing low pressure 

systems tapping into subtropical moisture. This shift created 

some significant rainfall over portions of the subbasin that 

exacerbated flooding (National Oceanic and Atmospheric 

Administration, 2012b) (figs. 3, 7, 8, and 9). 

Much of the lower Mississippi River subbasin received 

less than one-half of the December normal precipitation. 

For December 2010, Louisiana reported a statewide average 

monthly total of only 1.94 inches (table 1), resulting in the 

third driest December since 1895; however, Baton Rouge 

received 4.59 inches, or about 80 percent of normal December precipitation (table 2). Mississippi also had its third driest 

December on record with a monthly precipitation total of only 

1.55 inches (table 1). Areas in the western part of the subbasin, 

including Oklahoma City, reported only a small fraction of 

their normal December precipitation (National Oceanic and 

Atmospheric Administration, 2012c; table 2). 

January and February were mostly dry in the subbasin. 

In central Louisiana and southern Mississippi, most of the 

weather stations reported precipitation totals that ranged 

between one-quarter and one-half of normal. Baton Rouge had 

less than one-half of normal February precipitation. However, 

Oklahoma City had above normal February precipitation. The 

wettest area of the subbasin included much of north-central 

Arkansas, which had precipitation totals of 50 to 300 percent 

above normal in February (National Oceanic and Atmospheric 

Administration, 2012c). Several low pressure systems tracked 

across and to the north of this area interacting with warm, 

moist air from the Gulf of Mexico. Showers and thunderstorms that developed along the frontal boundaries resulted in 

areas of heavy rain.

March and April precipitation was variable throughout the subbasin. March precipitation was below normal in 

Arkansas, Louisiana, and Oklahoma and above normal in 

Mississippi and Tennessee. April precipitation was below normal in Louisiana and above normal in Arkansas, Mississippi, 

Oklahoma, and Tennessee (National Oceanic and Atmospheric 

Administration, 2012c; table 1). Texas had its second driest 

March on record (National Oceanic and Atmospheric Administration, 2012b), with a statewide average of 0.29 inches 

(table 1).

Hydrologic technicians working on the Mississippi River at Natchez, Mississippi, inspect the instrument mounted on the 

bow of the boat used to measure river velocity and depth. Photograph by Robert Holmes, U.S. Geological Survey.
Precipitation on the Mississippi River Basin 13

In April, Memphis had 12.58 inches of rainfall, or more 

than 100 percent above normal (table 2). The April rain in 

Memphis was part of a larger precipitation event that also 

included most of the Ohio River subbasin. The last half of 

April brought a slow moving weather pattern coupled with 

a quasi-stationary front over the Ohio River subbasin. As 

deep tropical moisture pushed northward, it interacted with 

this quasi-stationary frontal boundary over western Tennessee as well as with additional low pressure systems and their 

associated fronts moving through the Southern States. Numerous large thunderstorm complexes developed and propagated 

across the Central to Southern Plains, eventually moving into 

western Tennessee and northeast along the Ohio River subbasin. Rainfall totals were substantial; just less than 5 inches of 

rain fell in a 24-hour period in Memphis, and several locations 

reported amounts of 15 to 20 inches for the storm total precipitation. Areas in southeastern Missouri recorded more than 

20 inches of rain. Conversely, Texas had the fifth driest April 

on record (National Oceanic and Atmospheric Administration, 

2012b).

May was a mostly dry month in the lower Mississippi 

River subbasin (National Oceanic and Atmospheric Administration, 2012b). Much of the subbasin averaged less than 

one-half of normal precipitation for the month; however, in 

northern and central Arkansas, some locations reported nearly 

twice the normal values. Precipitation also was above normal 

for the areas around Memphis and in northeastern Oklahoma, 

including Oklahoma City (table 2).

Most areas of the subbasin recorded below-normal precipitation during June; however, during July, southern Louisiana and much of Mississippi had normal to above-normal precipitation. This occurrence was in part the result of cold fronts 

dropping southward and colliding with the warm, moist air 

from the Gulf of Mexico, which created thunderstorms with 

areas of rain along the frontal boundary (National Oceanic 

and Atmospheric Administration, 2012b). July precipitation 

totals in the subbasin ranged from normal to twice the normal 

amounts. Louisiana averaged 6.39 inches of precipitation for 

July, while Mississippi averaged 5.75 inches (table 1). During 

July, Baton Rouge had slightly above-normal precipitation, but 

farther north, Memphis had only about three-quarters of the 

normal precipitation (table 2).

Ohio River Subbasin

In the Ohio River subbasin mostly dry conditions during 

December and January were followed by very wet conditions 

for February through April. The heavy February through April 

precipitation caused flooding along the Ohio River and contributed to some of the earliest flooding on the lower Mississippi River in April 2011 (National Oceanic and Atmospheric 

Administration, 2011a, National Oceanic and Atmospheric 

Administration, 2012e). 

Precipitation during December and January was mostly 

below normal across the Ohio River subbasin (table 2). 

Precipitation increased during February and March, with 

above-normal amounts recorded at several locations, including Louisville and Cincinnati/Covington Airport (table 2). 

Six states that are partially within the Ohio River subbasin 

(Illinois, Indiana, Kentucky, Ohio, Pennsylvania, and West 

Virginia) reported the wettest April on record. 

During April 18–28, 2011, a series of storm systems 

produced large amounts of precipitation across much of the 

Ohio River subbasin and the northern portion of the lower 

Mississippi River subbasin along the border between Illinois 

and Missouri (National Oceanic and Atmospheric Administration, 2011d). Two primary weather features (fig. 12) 

contributed to the April 18–28, 2011, precipitation event. 

First, a high pressure region was strengthening across the 

far Southeastern States that pushed warm, moist air from the 

Gulf of Mexico northward across the lower Mississippi River 

subbasin. Second, a jet stream progressed from the northern 

Rocky Mountains southward into the Central Plains and then 

across the Ohio River subbasin through the Northeastern 

States. The position of the jet stream led to the development of 

low-pressure areas near the Texas and Oklahoma Panhandles. 

These low-pressure areas then moved slowly towards the 

northeast into the eastern Great Lakes. The clash of colder 

air in the Northern States with the warm, moist air from the 

south occurred in addition to these low-pressure areas, which 

generated large amounts of precipitation and severe weather, 

especially in the Midwestern United States. At several weather 

stations in this region, some precipitation was recorded almost 

every day during April 18–28, 2011 (National Oceanic and 

Atmospheric Administration, 2011d).

Precipitation totals during April 18–28, 2011, generally 

were very large across the Ohio River subbasin except for the 

extreme eastern and northeastern parts of the subbasin (figs. 1 

and 13). During the 11-day period, precipitation totals over 

8 inches were recorded at Terre Haute and Evansville, Indiana, 

Louisville, Kentucky, and Cincinnati, Ohio/Covington Airport, 

Ky. (table 3). At Cape Girardeau, Missouri, in the lower 

Mississippi River subbasin about 30 miles northwest of the 

Mississippi River and Ohio River confluence, an impressive 

11-day total of 16.15 inches was recorded. Monthly precipitation totals for April at some weather stations in the Ohio 

River subbasin (fig. 13) were more than 10 inches, or nearly 

one-quarter to one-half the average annual totals. April totals 

of 13.52 inches at Cincinnati/Covington Airport, 13.97 inches 

at Louisville, and 20.52 inches at Cape Girardeau were all 

records for the month (National Oceanic and Atmospheric 

Administration, 2011d). May and June total precipitation was 

near or above normal for most selected locations in the subbasin. In July, all selected locations reported near to belownormal precipitation (National Oceanic and Atmospheric 

Administration, 2011d).
14 Precipitation Contributing to the 2011 Flooding in the Mississippi River and Red River of the North Basins

A

TLANTIC

OCEAN

PA

CIF

CI OCEAN

GULF OF MEXICO

CANADA

Base from Esri digital data, 2000, 1:3,000,000

Albers Equal-Area Conic projection

Standard parallels 20°N and 60°N, central meridian 96°W

MEXICO

120°

110°

100° 80°

40°

30°

90°

70°

130°

L

L

H

EXPLANATION

Low atmospheric pressure area

High atmospheric pressure area

L

H

Moist air

Cool air

Approximate position of jet stream

0 200 400 600 MILES

0 400200 600 KILOMETERS

Figure 12. Approximate position of primary weather features that contributed to the 

April 18–28, 2011, precipitation event in the Ohio River subbasin.

Table 3. Summary of precipitation totals during the April 18–28, 2011, precipitation event1

, total precipitation for April 20111, 

the 1971–2000 normal April precipitation2

, and the 30-year average annual precipitation (1971–2000)2 for selected weather 

stations in and near the Ohio River subbasin.

Station

Precipitation, in inches

April 18–28, 2011 April 2011 April normal 

1971–2000

Average annual 

1971–2000

Cape Girardeau, Missouri 16.15 20.52 4.34 46.54

Cincinnati, Ohio/Covington Airport, Kentucky 8.03 13.52 3.96 42.60

Evansville, Indiana 8.23 11.77 4.48 44.27

Louisville, Kentucky 8.37 13.97 3.91 44.54

Memphis, Tennessee 9.74 12.58 5.36 53.63

Terre Haute, Indiana 8.05 11.01 4.12 42.47

1

National Oceanic and Atmospheric Administration (2011d).

2

National Oceanic and Atmospheric Administration (2012d).
Precipitation on the Mississippi River Basin 15

0

3

6

9

12

15

18

21

Total precipitation, in inches

April 18–28, 2011 April 2011 April normal,

1971–2000

0

3

6

9

12

15

18

21

Total precipitation, in inches

0

3

6

9

12

15

18

21

Total precipitation, in inches

April 18–28, 2011 April 2011 April normal,

1971–2000

A B

C D

E Dates

Dates

Figure 13. Precipitation totals during the April 18–28, 2011, 

precipitation event, total precipitation for April 2011, and the 

1971–2000 normal April precipitation for five locations in or 

near the Ohio River subbasin. A, Cape Girardeau, Missouri. 

B, Evansville, Indiana. C, Louisville, Kentucky. D, Cincinnati, 

Ohio/Covington Airport, Kentucky. E, Terra Haute, Indiana.

Photograph at left: Levee stoplogs 

in place on Illinois Route 34 at 

Harrisburg, Illinois. The levee system 

protects Harrisburg from backwater 

flooding from the Ohio River, more 

than 20 miles away. Photograph 

by Robert Holmes, U.S. Geological 

Survey.
16 Precipitation Contributing to the 2011 Flooding in the Mississippi River and Red River of the North Basins

Missouri River Subbasin

Extensive flooding occurred in the Missouri River subbasin during the spring and summer of 2011 (National Oceanic 

and Atmospheric Administration, 2011a; National Oceanic and 

Atmospheric Administration, 2012e). The flooding was caused 

by an exceptional snowpack produced by plentiful precipitation that fell December through April in the Rocky Mountain headwater areas and the plains of South Dakota, North 

Dakota, and Montana (figs. 4–8), and exceptional rainfall that 

fell throughout most of the subbasin during May through July 

(figs. 9–11). 

Several locations within the Missouri River subbasin had 

record snowfalls during the 2010–11 winter season (National 

Oceanic and Atmospheric Administration, 2011a). These 

record snowfalls were caused by moisture and low pressure 

troughs overriding cold continental polar air that blanketed 

the Northern Plains. At Glasgow, Montana, the seasonal 

snowfall record was established with 108.6 inches. The previous snowfall record was 70.7 inches set during the 2006–07 

season. Williston, N. Dak., received a record 107.2 inches of 

snow in 2010–11. The previous record was 94.7 inches set 

during the 1895–96 season. In Aberdeen, South Dakota, a new 

December snowfall record was established with 24.6 inches of 

snow compared to 24.1 inches in 1927. January and February 

snowfall amounts at Aberdeen were also higher than normal, resulting in a winter snowfall record of 61.2 inches, as 

compared to the previous record of 57.0 inches set in 1915. 

Winter precipitation was above or much above normal for 

most of the Missouri River subbasin (fig. 2). Some locations 

along the Missouri River in Montana and North Dakota had 

winter 2010–11 precipitation totals that ranged from more than 

135 percent to almost 280 percent above normal (National 

Oceanic and Atmospheric Administration, 2011d).

With little change in the overall weather pattern that dominated the winter months, snowfall continued into the spring 

months in the Rocky Mountains of Montana and Wyoming. 

Snow-water equivalents (SWE), determined on May 1, 2011, 

from SNOTEL (snowpack telemetry) sites operated by the 

U.S. Department of Agriculture Natural Resources Conservation Service, ranged from about 4 to 58 inches in subbasins of 

the Missouri River subbasin in Montana and Wyoming (Natural Resources Conservation Service, 2011a). Also on May 1, 

2011, almost one-half of the SNOTEL sites in Montana and 

Wyoming recorded SWE greater than 20 inches. SWE values 

were 111 to over 150 percent of average in most of the SNOTEL sites in the Missouri River subbasin (Natural Resources 

Conservation Service, 2011a). The Wyoming State Climate 

Office reported that statewide SWE topped 150 percent of 

normal at the end of April 2011 (Wyoming State Climate 

Office, 2011a). By the end of May, Wyoming statewide SWE 

topped 327 percent of normal (Wyoming State Climate Office, 

2011b). The large snowpack in the Rocky Mountains of Montana and Wyoming, combined with the large amounts of snow 

throughout the Northern Plains, made excessive amounts of 

runoff possible during spring and summer 2011.

Precipitation at the Missouri River subbasin locations in 

Rapid City, S. Dak., Williston, North Dakota, and Great Falls, 

Mont., was near to above normal for the months of December, 

January, February, April, and May (table 2). Most of Nebraska 

had normal precipitation during December through February 

and above-normal precipitation during March–May (figs. 2 

and 3).

During May 16–31, a large high-pressure area strengthened over the southeastern third of the country that resulted 

in hot, dry weather in the Southern United States (Hydrometeorological Prediction Center, 2012). Meantime, a large low 

pressure trough moved into the west. This trough was cool, 

moist, slow-moving, and strong. Furthermore, the significant 

moisture already associated with the system was increased as 

the trough tapped into moist air from the Southern Plains and 

the Gulf of Mexico. As the low passed to the south and east 

of Montana, isentropic processes—warm, moist air overriding the cooler air—produced substantial, and even record 

breaking, precipitation amounts to parts of the Northern Plains 

(fig. 14). As the rainfall was occurring in the northern portion 

of the system, the cold front was tracking further south across 

the Central and Northern Plains with widespread thunderstorms along the frontal boundary. With the excessive atmospheric moisture available, this front produced widespread 

areas of heavy rain, which were further enhanced by the slow 

moving nature of the system. 

May 2011 precipitation amounts at some locations in 

the Missouri River subbasin were almost as large as normal 

annual totals (National Oceanic and Atmospheric Administration, 2011d). Mildred, Mont., about 50 miles northeast of Miles City, Mont. (fig. 1), reported 10.14 inches of 

rain for May, relative to the normal annual precipitation of 

12.63 inches. Rock Springs, Mont., located about 35 miles 

northwest of Miles City, reported 10.46 inches of rain, 

relative to the normal annual precipitation of 11.67 inches. 

Farther west at Great Falls, Mont., the May 2011 precipitation 

Snow bank in Wyoming, June 2011. Photograph by Paul Thatch, Wyoming 

Department of Transportation.
Precipitation on the Mississippi River Basin 17

A

TLANTIC

OCEAN

PA

CIF

CI OCEAN

GULF OF MEXICO

CANADA

MEXICO

120°

110°

100° 80°

40°

30°

90°

70°

130°

L

L

H

Approximate position of jet stream

EXPLANATION

Low atmospheric pressure area

High atmospheric pressure area

L

H

Moist air

Cool air

Uplift

0 200 400 600 MILES

0 400200 600 KILOMETERS

Base from Esri digital data, 2000, 1:3,000,000

Albers Equal-Area Conic projection

Standard parallels 20°N and 60°N, central meridian 96°W

Figure 14. Approximate position of primary weather features that contributed to the 

May 16–31, 2011, rainfall event in the Missouri River subbasin.

total was also greater than normal, but by a smaller amount 

(National Oceanic and Atmospheric Administration, 2011d). 

In the mountains of Montana, snow fell during the May 16–31 

storm, particularly in the headwaters of the Yellowstone River. 

Throughout the month of May, there was some snow accumulation in the mountains of Montana into late May. Total May 

2011 precipitation values at Rapid City, S. Dak., and Williston, 

N. Dak., were more than double of May normal precipitation 

values (table 4). 

Precipitation totals recorded during May 16–31, 2011, 

included over 6 inches at Billings and Baker, Mont., and Rapid 

City, S. Dak., during the 16-day event (National Oceanic and 

Atmospheric Administration, 2011d) (fig. 15, table 4). Most 

of the weather stations in Montana, North Dakota, South 

Dakota, and Wyoming recorded precipitation on at least 14 of 

the 16 days (National Oceanic and Atmospheric Administration, 2011d). Billings, Miles City, Baker, and Glasgow, Mont., 

and Rapid City, S. Dak., had precipitation totals during the 

May 16–31 event that were at least twice the normal precipitation for May. All five locations had precipitation totals during 

May 16–31 that were about one-third to one-half of their 

1971–2000 normal annual amounts. 

The areally-averaged May 2011 precipitation in the Missouri River subbasin, upstream from Garrison Dam, N. Dak., 

was determined to be 6 inches using radar estimates coupled 

with rain gage precipitation amounts by the National Weather 

Service River Forecast Centers (National Oceanic and 

Atmospheric Administration, 2011b). This precipitation fell 

mostly as rain over the plains with some rain and snow over 

the mountains. If this depth of precipitation was assumed to 
18 Precipitation Contributing to the 2011 Flooding in the Mississippi River and Red River of the North Basins

Table 4. Summary of precipitation totals during the May 16–31, 2011, precipitation event1, total precipitation for May 20111, the 1971–

2000 normal May precipitation2

, and the 30-year average annual precipitation (1971–2000)2 for selected weather stations in the Missouri 

River subbasin.

Station Precipitation, in inches

May 16–31, 2011 May 2011 May normal 1971–2000 Average annual 1971–2000

Baker, Montana 6.09 7.34 2.09 14.38

Billings, Montana 6.63 9.54 2.48 14.77

Glasgow, Montana 5.21 6.97 1.72 11.23

Miles City, Montana 5.79 9.36 2.19 13.49

Rapid City, South Dakota 7.61 8.24 2.96 16.64

Williston, North Dakota 2.91 5.28 1.88 14.16

1

National Oceanic and Atmospheric Administration (2011d).

2

National Oceanic and Atmospheric Administration (2012d).

have fallen across the 181,400-square mile portion of the Missouri River subbasin upstream from Garrison Dam, then the 

estimated volume of water that fell on that part of the subbasin 

was about 58,000,000 acre-feet. For comparison purposes, the 

combined volume of conservation pool capacities for the two 

Missouri River main stem reservoirs upstream from Garrison 

Dam, Fort Peck Reservoir in Montana, and Lake Sakakawea 

in North Dakota is about 42,300,000 acre-feet (U.S. Army 

Corps of Engineers, 2012a). The May 2011 precipitation plus 

the runoff that was occurring as a result of a record snowpack 

in the subbasin produced enormous volumes of flow in the 

subbasin.

Precipitation amounts in June and July 2011 were 

relatively large in much of South Dakota, North Dakota, and 

Montana (figs. 10 and 11). Similar to May 2011, some areas of 

northeastern Montana received about twice the normal precipitation in June and July. Glasgow, Mont., reported 9.70 inches 

of precipitation or about 5.5 inches above normal during June 

and July 2011 (National Oceanic and Atmospheric Administration, 2011d). These occasional large amounts of precipitation 

during early summer on the Missouri River subbasin contributed to flooding conditions along the Missouri River.

Upper Mississippi River Subbasin

December and January precipitation was variable across 

the upper Mississippi River subbasin. Springfield, Ill., and 

Madison, Wis., had below to near normal precipitation while 

Chanhassen, Minn., had above-normal precipitation (table 2). 

The above-normal precipitation was due in large part to a 

mid-December storm, the seventh in a series of snowstorms to 

hit Minnesota in less than 2 months. The storm was initiated 

by a low pressure system working its way across Southern 

Canada. As the associated cold front was moving through the 

Upper Midwest, a secondary low developed along the cold 

front near the Minnesota/Iowa border, intensifying as it moved 

to the east. The intensification strengthened the inflow, feeding 

moisture into the storm system from the south. Snowfall with 

the storm was significant enough that snowplows were called 

off the roadways, and many roads were closed. This was the 

greatest snowfall for the area in nearly 20 years, and the fifth 

largest snowfall at the Minneapolis-St. Paul International 

Airport. Two more storms hit the area in December, and at 

the end of the month, Minnesota had recorded the third wettest December on record (National Oceanic and Atmospheric 

Administration, 2012b). Some weather stations in Wisconsin 

and Minnesota reported snowfalls of 36 inches to 48 inches in 

December while other stations in Iowa and Minnesota reported 

a maximum snow depth on the ground of at least 24 inches 

during the month. January snowfall was more than 100 percent 

above normal from northwestern Minnesota through northern 

Iowa (National Oceanic and Atmospheric Administration, 

2011a).

Through the remainder of winter and into spring, cold 

continental polar air continued to filter into the Northern 

Plains from Canada, and moisture worked its way into the area 

from low pressure systems pushing through from the west or 

from a tap into subtropical moisture from the Gulf of Mexico. 

January snowfall was more than 100 percent above normal 

from northwestern Minnesota through northern Iowa (National 

Oceanic and Atmospheric Administration, 2011a). February, 

March, and April precipitation was normal to above normal for 

Madison, Wisconsin, and Chanhassen, Minnesota, and February and April precipitation was above normal for Springfield, 

Illinois. March snowfall exceeded 24 inches from southern 

Minnesota to across much of Wisconsin. Some of the earliest major flooding in 2011 occurred in Minnesota along the 

upper Mississippi River in March 2011 as the result of rapid 

snowmelt and spring rains (National Oceanic and Atmospheric 

Administration, 2011a; National Oceanic and Atmospheric 

Administration, 2012e). 

As the seasons shifted to late spring and summer, the tap 

into moist, unstable subtropical air increased. These systems 
Precipitation on the Mississippi River Basin 19

Photograph at left: Flooding of the Sun River in the town of Sun River, Montana, 

June 9, 2011. Photograph by Michael Mercer, Meteorologist in Charge, Great 

Falls Weather Forecast Office, National Weather Service.

0

2

4

6

8

10

0

2

4

6

8

10

0

2

4

6

8

10

Total precipitation, in inches

May 16–31, 2011 May 2011 May normal,

1971–2000

Total precipitation, in inches Total precipitation, in inches

May 16–31, 2011 May 2011 May normal,

1971–2000

A B

C D

E F

Dates Dates

Figure 15. Precipitation totals during the May 16–31, 2011, precipitation event, precipitation totals for May 2011, and the 1971–2000 

normal May precipitation for six locations in the Missouri River subbasin. A, Billings, Montana. B, Baker, Montana. C, Rapid City, South 

Dakota. D, Miles City, Montana. E, Glasgow, Montana. F, Williston, North Dakota.
20 Precipitation Contributing to the 2011 Flooding in the Mississippi River and Red River of the North Basins

were now producing areas of stratiform clouds and rain with 

areas of heavier convective precipitation as thunderstorms 

developed along frontal boundaries. Much of the subbasin 

received normal to above-normal precipitation during May, 

with the exception of Wisconsin and northeastern Minnesota, 

where precipitation was slightly below normal (National Oceanic and Atmospheric Administration, 2011a).

June and July precipitation was above normal across a 

large portion of the subbasin (figs. 10 and 11). June precipitation was two-to-three times normal in parts of Iowa. On 

more than one occasion, very moist air would overrun a slow 

moving or stalled cold front resulting in areas of heavy precipitation. Near the end of June, a high pressure ridge became 

centered over the south-central and southeastern United States. 

Warm, moist subtropical air was now available to the Northern Plains by means of the Southwest Monsoon and a tap into 

air off the Gulf of Mexico. As low pressure systems moved 

through, this moist air fueled the development of areas of 

heavy rain, primarily as strong thunderstorms developed along 

the frontal boundaries. July precipitation was nearly twice 

normal from west-central Minnesota into western Wisconsin. Below normal July precipitation at Springfield, Ill., and 

Madison, Wis., reflected the northern extent of the strong high 

pressure system that was in place over the Southern Plains. 

July precipitation was above normal at Chanhassen, Minn., 

in response to storms moving around the strong high pressure 

system (National Oceanic and Atmospheric Administration, 

2011a).

Precipitation on the Red River of the 

North Basin

Portions of the Red River of the North Basin, including 

the Souris River, often flood during spring when snowmelt 

that cannot infiltrate frozen or saturated soils runs off into 

rivers that flow north. Those portions of the rivers that are 

further north are slower to lose their ice cover, in effect creating a dam to water moving in from the south. During 2011, 

saturated soils from a wet autumn and abundant snow and the 

presence of river ice and large amounts of precipitation during 

spring and summer contributed to high flows and flooding in 

the Red River of the North and the Souris River (Minnesota 

Climatology Working Group, 2011). Grand Forks, N. Dak., 

reported 55.5 inches of snow during November 2010–May 

2011, as compared to the 1971–2000 normal of 47.0 inches 

(National Oceanic and Atmospheric Administration, 2011e). 

Precipitation totals in parts of North Dakota and northwestern Minnesota were greater than two times normal amounts 

in April through June (High Plains Regional Climate Center, 

2011a, b, c, d). 

During the last two weeks of June 2011, there was a noteworthy precipitation event someplace in North Dakota almost 

daily (High Plains Regional Climate Center, 2011c). This area 

was hit by a series of low pressure troughs during this period, 

steered across the Northern Plains by a building high pressure 

ridge over the Southern States. Thunderstorms that would 

develop along the frontal boundaries were often slow moving 

and would train over the same area. With an abundant supply 

of atmospheric moisture, these storms created areas of very 

substantial rainfall. June precipitation was higher than normal 

at Fargo and Grand Forks, N. Dak., but was slightly lower 

than normal at Minot, N. Dak. (table 2). Regina, near the 

headwaters of the Souris River in southeastern Saskatchewan, 

Canada, had a June precipitation total of 5.2 inches, compared 

to a June normal (1971–2000) total precipitation of 3.0 inches 

(Environment Canada, 2011). Large amounts of precipitation 

continued through July at Fargo and Minot, N. Dak., but July 

precipitation at Grand Forks, N. Dak. was less than normal. 

Summary

 Excessive precipitation produced severe flooding in the 

Mississippi River and Red River of the North Basins during 

spring and summer 2011. The flooding resulted from weather 

conditions during December 2010 through July 2011 that were 

affected in part by a La Niña climate pattern. This pattern is 

characterized by cooler-than-average sea surface temperatures 

in the central and east-central equatorial Pacific Ocean, and a 

strong high pressure area in the northern Pacific Ocean region. 

The La Niña pattern tends to produce cooler and wetter than 

normal weather conditions over the western and north-central 

regions of the Mississippi River and Red River of the North 

Basins, and often warmer and drier than normal weather conditions over the southern Mississippi River Basin. 

Precipitation patterns across the Red River of the North 

and Mississippi River Basins from December 2010 through 

July 2011 followed the mean position of the jet stream. During 

December, January, and February, a southward push of the jet 

stream steered several low pressure troughs across the country 

from the Rocky Mountains into the Ohio River subbasin 

producing large amounts of precipitation. From March through 

May, a large low pressure trough dominated the continental 

States, and a high pressure ridge was centered in the vicinity 

of the Gulf of Mexico. This weather combination produced 

storms with copious precipitation along frontal boundaries 

that were steered across the Central States. During June and 

July, moisture from the southwestern monsoon and the Gulf 

of Mexico worked its way into the Plains States. Low pressure troughs moving across the country interacted with this 

moist unstable air; thunderstorm development along frontal 

boundaries resulted in areas of heavy rain across the Northern 

Plains States into the Missouri and upper Mississippi River 

subbasins. Excessive precipitation that fell on already saturated ground and ran off into already full streams and rivers 

produced severe flooding in the Mississippi River and Red 

River of the North Basins during spring and summer 2011.
References Cited 21

Much of the lower Mississippi River subbasin had belownormal precipitation during December, January, and February. 

March precipitation was below normal in Arkansas, Louisiana, 

and Oklahoma, and above normal in Mississippi and Tennessee. April precipitation was below normal in Louisiana 

and above normal in Arkansas, Mississippi, Oklahoma, and 

Tennessee. In April, Memphis had 12.58 inches of rainfall that 

resulted from deep tropical moisture that pushed northward 

and interacted with this quasi-stationary frontal boundary over 

western Tennessee. Additional low pressure systems and their 

associated fronts moved through the region resulting in numerous large thunderstorm complexes. Conversely, Texas had the 

fifth driest April on record. May and June were mostly dry, 

but in July, southern Louisiana and much of Mississippi had 

normal to above-normal precipitation.

Precipitation across the Ohio River subbasin during 

December and January was mostly below normal, but precipitation increased during February and March, with several locations receiving above-normal amounts. During April, a high 

pressure region was strengthening across the far Southeastern 

States that pushed warm, moist air from the Gulf of Mexico 

northward. A jet stream progressed from the northern Rocky 

Mountains southward into the Central Plains and then across 

the Ohio River subbasin through the Northeastern United 

States. The position of the jet stream led to the development 

of low-pressure areas near the Texas and Oklahoma Panhandles. These low-pressure areas then moved slowly towards 

the northeast into the eastern Great Lakes, which generated 

large amounts of precipitation and severe weather. Rain totals 

recorded during the April 18–28, 2011, precipitation event 

were over 8 inches at several locations, while an impressive 

total of 16.15 inches was recorded at Cape Girardeau, Missouri. Monthly precipitation totals for April at some weather 

stations in the Ohio River subbasin were more than 10 inches, 

or nearly one-quarter to one-half the average annual totals. 

May and June total precipitation was near or above normal for 

most selected locations in the subbasin. In July, all selected 

locations reported near to below-normal precipitation.

Several locations within the Missouri River subbasin had 

record snowfalls during the 2010–11 winter season. The frequent influx of moisture moving in with low pressure troughs 

then overriding the cold continental polar air that blanketed 

the Northern Plains during much of the climatological winter 

resulted in the record snowfall. Some locations in Montana 

and North Dakota recorded precipitation totals of more than 

135 percent to almost 280 percent above normal. During the 

May 16–31 precipitation event, several locations in the Missouri River subbasin had rainfall totals that were nearly onethird to one-half of their 1971–2000 normal annual amounts. 

Precipitation amounts in June and July 2011 were relatively 

large in much of South Dakota, North Dakota, and Montana. 

Some areas of northeastern Montana received about twice the 

normal June and July precipitation. 

December and January precipitation was variable across 

the upper Mississippi River subbasin. Springfield, Illinois, and 

Madison, Wisconsin, had below to near-normal precipitation 

while Chanhassen, Minnesota, had above normal precipitation. 

March snowfall exceeded 24 inches from southern Minnesota 

to across much of Wisconsin. Much of the subbasin received 

normal to above normal rainfall during May, with the exception of Wisconsin and northeastern Minnesota, where precipitation was slightly below normal. June and July precipitation 

was above normal across a large portion of the subbasin. Very 

moist air would overrun a slow moving or stalled cold front 

resulting in areas of substantial precipitation. Near the end of 

June, the presence of a high pressure ridge centered over the 

South-Central and Southeastern United States, and a flow of 

warm, moist air from the Gulf of Mexico fueled the development of areas of strong thunderstorms and rain along frontal 

boundaries. July precipitation was nearly twice normal from 

west-central Minnesota into western Wisconsin. Below-normal 

July precipitation at Springfield, Ill., and Madison, Wis., 

reflected the northern extent of the strong high pressure system 

that was in place over the Southern Plains. 

Portions of the Red River of the North Basin, including 

the Souris River, often flood during spring when snowmelt 

that cannot infiltrate frozen or saturated soils runs off into 

rivers that flow north. Grand Forks, North Dakota, reported 

55.5 inches of snow during November 2010–May 2011, as 

compared to the 1971–2000 normal of 47.0 inches. Precipitation totals in parts of North Dakota and northwestern Minnesota were greater than two times normal amounts in April 

through June. During the last two weeks of June 2011, this 

area was hit by a series of low pressure troughs. Thunderstorms that would develop along the frontal boundaries were 

often slow moving and would train over the same area. With 

an abundant supply of atmospheric moisture, these storms 

created areas of very substantial rainfall. June precipitation 

was higher than normal at Fargo and Grand Forks, N. Dak. 

Regina, near the headwaters of the Souris River in southeastern Saskatchewan, Canada, had a June precipitation total 

of 5.2 inches, compared to a June normal (1971–2000) total 

precipitation of 3 inches. Large amounts of precipitation continued through July at Fargo and Minot, N. Dak.

References Cited

Critchfield, H.J., 1974, General climatology (3d ed.): Englewood Cliffs, New Jersey, Prentice-Hall, Inc., 446 p.

Environment Canada, 2011, National climate data and information archive, accessed April 30, 2012, at http://www.

climate.weatheroffice.gc.ca/climateData/dailydata_e.html?

Prov=SK&StationID=28011&Year=2011&Month=6&Day

=30&timeframe=2.
22 Precipitation Contributing to the 2011 Flooding in the Mississippi River and Red River of the North Basins

High Plains Regional Climate Center, 2011a, April 2011 

climate summary, accessed September 1, 2011, at http://

www.hprcc.unl.edu/publications/files/2011_04_climatesummary.pdf.

High Plains Regional Climate Center, 2011b, May 2011 

climate summary, accessed September 1, 2011, at http://

www.hprcc.unl.edu/publications/files/2011_05_climatesummary.pdf.

High Plains Regional Climate Center, 2011c, June 2011 

climate summary, accessed September 1, 2011, at http://

www.hprcc.unl.edu/publications/files/2011_06_climatesummary.pdf.

High Plains Regional Climate Center, 2011d, Climate summary maps, accessed September 1, 2011, at http://www.

hprcc.unl.edu/maps/current/index.php?action=update_

userdate&daterange=AMJ&year=11.

Hydrometeorological Prediction Center, 2012, Daily weather 

maps, accessed September 2012, at http://www.hpc.ncep.

noaa.gov/dailywxmap/index.html.

Minnesota Climatology Working Group, 2011, March 2011 

HydroClim Minnesota newsletter, accessed March 22, 2012, 

at http://climate.umn.edu/doc/journal/hc1103.htm.

National Oceanic and Atmospheric Administration, 2002, 

Historical climatography series 4–2, area-weighted monthly 

normals, 1971–2000 (and previous periods): Asheville, 

North Carolina, National Climatic Data Center, 17 p.

National Oceanic and Atmospheric Administration, 2010, 

NOAA: Another winter of extremes in store for U.S. as 

La Niña strengthens, accessed August 2011, at http://www.

noaanews.noaa.gov/stories2010/20101021_winteroutlook.

html.

National Oceanic and Atmospheric Administration, 2011a, 

State of the climate: National Oceanic and Atmospheric 

Administration, National Climatic Data Center, accessed 

August 2011, under various web pages for various precipitation variables and months at http://www.ncdc.noaa.gov/

sotc/.

National Oceanic and Atmospheric Administration, 2011b, 

Advanced hydrologic prediction service precipitation download, accessed August 2011, at http://water.weather.gov/

precip/download.php.

National Oceanic and Atmospheric Administration, 2011c, 

Interactive snow information: National Operational Hydrologic Remote Sensing Center , accessed August 2011, at 

http://www.nohrsc.noaa.gov/interactive/html/map.html.

National Oceanic and Atmospheric Administration, 2011d, 

National Weather Service online weather data, accessed 

September 1, 2011, under various web pages for various 

locations at http://www.nws.noaa.gov/climate/.

National Oceanic and Atmospheric Administration, 2012a, 

Performance Management Branch, Performance Management Homepage, accessed September 13, 2012, at https://

verification.nws.noaa.gov/.

National Oceanic and Atmospheric Administration, 2012b, 

National temperature and precipitation maps, accessed 

April 27, 2012, under various web pages for various months 

at http://www.ncdc.noaa.gov/temp-and-precip/maps.php.

National Oceanic and Atmospheric Administration, 

2012c, Monthly precipitation data by State, accessed 

March 22, 2012, at http://www7.ncdc.noaa.gov/CDO/

CDODivisionalSelect.jsp.

National Oceanic and Atmospheric Administration, 2012d, 

U.S. Climate normals: National Oceanic and Atmospheric 

Administration, National Climatic Data Center, accessed 

April 30, 2012, at http://hurricane.ncdc.noaa.gov/cgi-bin/

climatenormals/climatenormals.pl.

National Oceanic and Atmospheric Administration, 2012e, 

Service Assessment, spring 2011 middle & lower Mississippi River Valley floods: National Oceanic and Atmospheric Administration, National Weather Service, accessed 

December 10, 2012, at http://www.nws.noaa.gov/om/

assessments/pdfs/MisssissippiRiverFloods12.pdf.

Natural Resources Conservation Service, 2011a, SNOTEL 

update report, accessed August 2011, at http://www.wcc.

nrcs.usda.gov/reports/SelectUpdateReport.html.

U.S. Army Corps of Engineers, 2012a, Omaha District 

Lakes and Dams, accessed October 20, 2012, at http://

www.nwd-mr.usace.army.mil/rcc/reports/showrep.

cgi?3MRDTAP7

U.S. Army Corps of Engineers, 2012b, The Mississippi drainage basin, accessed June 4, 2012, at http://www.mvn.usace.

army.mil/bcarre/missdrainage.asp.

Watermolen, John, 2005, National atlas of the United States, 

version 2.4: Reston, Virginia, 1:2,000,000-scale hydrologic 

unit boundaries.

Wyoming State Climate Office, 2011a, Wyoming’s climate—

April 2011 summary, accessed April 30, 2012, at http://

www.wrds.uwyo.edu/sco/data/climate_summaries/Climate_

Summary_2011Apr.html.

Wyoming State Climate Office, 2011b, Wyoming’s climate—

May 2011 summary, accessed April 30, 2012, at http://

www.wrds.uwyo.edu/sco/data/climate_summaries/Climate_

Summary_2011May.html.
Publishing support provided by: 

Rolla Publishing Service Center

For more information concerning this publication, contact: 

Chief, USGS Office of Surface Water 

415 National Center 

12201 Sunrise Valley Drive 

Reston, VA 20192 

(703) 648-5301

Or visit the Office of Surface Water Web site at: 

http://water.usgs.gov/osw/
Vining and others—Precipitation Contributing to the 2011 Flooding in the Mississippi River and Red River of the North Basins—Professional Paper 1798–B