A nearly stationary west to east frontal boundary was located across Nebraska and Iowa for several days.  With an extremely moist atmosphere featuring near record precipitable water in place, several weak disturbances resulted in prolific rainfall from 3 to as much as 10 inches.  Sioux Falls, South Dakota established a new 24-hour rainfall record of 5.07 ending 1600LST September 20, as well as daily records for both September 19 and 20.

Flood in MOODY, SOUTH DAKOTA
From 21-SEP-18 03:00:00 to 22-SEP-18 03:00:00 (CST-6)
Location: FLANDREAU
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Crop and pasture land was inundated, as well as portions of the Flandreau Golf Course, as levels on Flandreau Creek above Flandreau climbed to 1.1 feet above flood stage (gage site FCRS2) on September 21. The river returned quickly below flood stage on September 22.

Flood in MOODY, SOUTH DAKOTA
From 20-SEP-18 16:00:00 to 22-SEP-18 01:00:00 (CST-6)
Location: FLANDREAU MUNI ARPT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Heavy rainfall on September 18-20 brought a widespread 3 to 5 inches of rainfall with 4.66 inches at Pipestone. Minor flooding occurred with crop and pasture land inundated as the North Branch of Pipestone Creek near Pipestone (gage site PSTM5) crested 0.4 foot above flood stage on September 21 at 0200LST.

Flood in UNION, SOUTH DAKOTA
From 20-SEP-18 19:00:00 to 23-SEP-18 10:00:00 (CST-6)
Location: SPINK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

For the second time in the month, heavy rainfall occurred across the Brule Creek basin from September 19-21, bringing 3 to 5 inches accumulation and moderate flooding.  478th Avenue and several other township roads across Emmett township were inundated  by water as Brule Creek near Richland (gage site BCKS2) crested 3.9 feet above flood stage around 0900LST on September 22.

Flood in MINNEHAHA, SOUTH DAKOTA
From 22-SEP-18 03:00:00 to 26-SEP-18 07:00:00 (CST-6)
Location: RENNER
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

With areas north of Sioux Falls just on the northern edge of heaviest rainfall from September 18-20, amounts generally 4 to 7 inches resulted in minor flooding of crop and pasture land around 60th Street North and Interstate 90. The Big Sioux River at Interstate 90 near Sioux Falls (gage site SFLS2) crested 0.9 feet above flood stage on September 23. The river dropped below flood stage on September 26.

Flood in MINNEHAHA, SOUTH DAKOTA
From 20-SEP-18 06:00:00 to 22-SEP-18 09:00:00 (CST-6)
Location: SOUTH SIOUX FALLS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Rainfall across the Sioux Falls metro area from September 18-20 totaled generally 5 to 7 inches. Moderate flooding resulted with significant inundation of city parks. The Big Sioux River at Western Avenue (gage site WAVS2) crested 4.0 feet above flood stage during the early overnight on September 21. The river dropped below flood stage on September 22.

Flood in LINCOLN, SOUTH DAKOTA
From 20-SEP-18 06:00:00 to 22-SEP-18 09:00:00 (CST-6)
Location: SIOUX FALLS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Rainfall across the Sioux Falls metro area from September 18-20 totaled generally 5 to 7 inches. Moderate flooding resulted with significant inundation of city parks. The Big Sioux River at Western Avenue (gage site WAVS2) crested 4.0 feet above flood stage during the early overnight on September 21. The river dropped below flood stage on September 22.

Flood in MINNEHAHA, SOUTH DAKOTA
From 21-SEP-18 00:00:00 to 21-SEP-18 14:00:00 (CST-6)
Location: NORTON ACRES
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Rainfall across the Sioux Falls metro area from September 18-20 totaled generally 4 to 7 inches. Minor flooding resulted along the Big Sioux River with crop and pasture land downstream of Sioux Falls impacted by flood waters as the Big Sioux River at North Cliff Avenue in Sioux Falls (gage site SXFS2) briefly crested 0.1 foot above flood stage on September 21.

Flood in MINNEHAHA, SOUTH DAKOTA
From 20-SEP-18 09:00:00 to 26-SEP-18 08:00:00 (CST-6)
Location: BRANDON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Rainfall across the Sioux Falls metro area from September 18-20 totaled generally 5 to 7 inches. Moderate flooding resulted with significant flooding of crop and pasture land as the Big Sioux River at Brandon (gage site BBSS2) crested 3.3 feet above flood stage on September 21.

Flood in LINCOLN, SOUTH DAKOTA
From 20-SEP-18 09:00:00 to 26-SEP-18 08:00:00 (CST-6)
Location: SHINDLER
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Rainfall across the Sioux Falls metro area from September 18-20 totaled generally 5 to 7 inches. Moderate flooding resulted with significant flooding of crop and pasture land as the Big Sioux River at Brandon (gage site BBSS2) crested 3.3 feet above flood stage on September 21.

Flood in LINCOLN, SOUTH DAKOTA
From 20-SEP-18 11:00:00 to 25-SEP-18 15:00:00 (CST-6)
Location: FAIRVIEW
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Rainfall across the Sioux Falls area and southward in the Big Sioux basin from September 18-20 totaled generally 5 to 7 inches. Major flooding resulted with all crop and pasture land in the half-mile wide flood plain inundated. The Big Sioux River above Canton (gage site CBSS2) crested 6.0 feet above flood stage on September 22, the third highest crest on record.

Flood in LINCOLN, SOUTH DAKOTA
From 20-SEP-18 13:00:00 to 26-SEP-18 08:00:00 (CST-6)
Location: HUDSON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Rainfall across the Sioux Falls area and southward in the Big Sioux basin from September 18-20 totaled generally 5 to 7 inches. Moderate flooding resulted with all crop and pasture land in the half-mile wide flood plain inundated as the Big Sioux River at Fairview (gage site FVWS2) crested 6.7 feet above flood stage on September 22.

Flood in UNION, SOUTH DAKOTA
From 20-SEP-18 03:00:00 to 30-SEP-18 03:00:00 (CST-6)
Location: ALCESTER
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Widespread upstream rainfall in the Big Sioux basin from September 18-20 totaled generally 5 to 10 inches, resulting in major flooding. South Dakota Highway 46 was closed, with several farm houses isolated by high water as the Big Sioux River above Hawarden (gage site HWDI4) crested 11.1 feet above flood stage on September 22.

Flood in UNION, SOUTH DAKOTA
From 20-SEP-18 18:00:00 to 30-SEP-18 23:59:00 (CST-6)
Location: BIG SPGS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Widespread upstream rainfall in the Big Sioux basin from September 18-20 totaled generally 5 to 10 inches, resulting in major flooding. South Dakota Highway 48 was closed with several farm houses inundated by high water, as the Big Sioux River at Akron (gage site AKRI4) crested 6.2 feet above flood stage on September 23.  Highway 48 was reopened on September 27, but the river remained in minor flood stage at the end of the month.

Flood in UNION, SOUTH DAKOTA
From 21-SEP-18 07:00:00 to 30-SEP-18 23:59:00 (CST-6)
Location: RICHLAND
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Widespread upstream rainfall in the Big Sioux basin from September 18-20 totaled generally 5 to 10 inches, resulting in major flooding. A few farm buildings were flooded with widespread crop and pasture land flooding as the Big Sioux River near Richland (gage site BSRS2) crested 6.2 feet above flood stage on September 23.  The river remained in minor flood stage at the end of the month.

Flood in UNION, SOUTH DAKOTA
From 23-SEP-18 12:00:00 to 27-SEP-18 18:00:00 (CST-6)
Location: ELK PT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Widespread upstream rainfall in the Big Sioux basin from September 18-20 totaled generally 5 to 10 inches, with downstream routing resulting in minor flooding. Significant flooding of crop and pasture land occured as the Big Sioux River near Jefferson (gage site BSJS2) crested 4.8 feet above flood stage on September 25.

Flood in MINNEHAHA, SOUTH DAKOTA
From 20-SEP-18 15:00:00 to 21-SEP-18 10:00:00 (CST-6)
Location: HARTFORD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Rainfall around the Sioux Falls metro area from September 18-20 totaled generally 5 to 7 inches. Minor flooding impacted mainly rural agricultural land, but water did start flowing over West 12th Street west of Sertoma Avenue along with some lowland flooding of city parks. Skunk Creek at Sioux Falls (gage site SIFS2) crested 1.0 foot above flood stage on September 21.

Flood in MINNEHAHA, SOUTH DAKOTA
From 20-SEP-18 04:00:00 to 22-SEP-18 20:00:00 (CST-6)
Location: LYONS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Rainfall across the Sioux Falls metro area from September 18-20 totaled generally 5 to 7 inches. Minor flooding impacted mainly pasture land as Willow Creek near Crooks (gage site WCCS2) crested 1.9 feet above flood stage on September 20.

Flood in MINNEHAHA, SOUTH DAKOTA
From 20-SEP-18 07:00:00 to 26-SEP-18 04:00:00 (CST-6)
Location: SHERMAN
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

Heavy rainfall on September 18-20 brought a widespread 3 to 5 inches of rainfall with 4.66 inches at Pipestone. Moderate flooding occurred with crop and pasture land inundated, as well as the low water crossing on 250th Street near the South Dakota border, as Split Rock Creek below Jasper (gage site JSPM5) crested 4.6 feet above flood stage at 0200LST on September 21, with a lesser secondary crest at 2200LST on September 21. The river dropped below flood stage on September 26.

Flood in MINNEHAHA, SOUTH DAKOTA
From 20-SEP-18 13:00:00 to 23-SEP-18 12:00:00 (CST-6)
Location: GARRETSON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: River/Stream Gage

With areas north of Sioux Falls just on the northern edge of heaviest rainfall from September 18-20, amounts generally 4 to 7 inches resulted in moderate flooding of agricultural land. Split Rock Creek near Corson (gage site COSS2) crested 3.7 feet above flood stage on September 21, and dropped below flood stage on September 23.