Flash Flooding and Hail in South Dakota, April 21 to 22, 2007

Name: Flash Flooding and Hail in South Dakota, April 21 to 22, 2007
Start: 2007-04-21T18:55
End: 2007-04-22T02:30
Location: South Dakota

April 21 to 22, 2007 · NWS ABR · 16 events in 4 counties and zones

A warm front extending across the region was the focus for heavy rain along with severe weather during the evening across far northeast South Dakota. Hail up to the size of quarters along with heavy rains of over 2 inches caused some flooding mainly in Codington and Hamlin counties.

Where it happened

Every event with a place to put it. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 16

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS ABR wrote it up.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Aberdeen, SD wrote its last area forecast discussion before the first event at Apr 21, 2:38 PM CST, 4 hours 17 minutes earlier.

Area forecast discussion, Apr 21, 2:38 PM CST, 4 hours 17 minutes before

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Hazardous weather outlook, Apr 21, 2:56 PM CST, 3 hours 59 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ABERDEEN SD
356 PM CDT SAT APR 21 2007

SDZ003-015-222100-
CORSON-DEWEY-
256 PM MDT SAT APR 21 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
SOUTH DAKOTA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SHOWERS AND THUNDERSTORMS ARE POSSIBLE THIS EVENING. A FEW STORMS
MAY BE SEVERE WITH GUSTY WINDS AND HAIL BEING THE MAIN THREATS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS EVENING.

SDZ005>008-010-011-016>019-033>037-045-048-051-222100-
MCPHERSON-BROWN-MARSHALL-ROBERTS-EDMUNDS-DAY-POTTER-FAULK-SPINK-
CLARK-STANLEY-SULLY-HUGHES-HYDE-HAND-JONES-LYMAN-BUFFALO-
356 PM CDT SAT APR 21 2007 /256 PM MDT SAT APR 21 2007/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL SOUTH
DAKOTA...NORTH CENTRAL SOUTH DAKOTA AND NORTHEAST SOUTH DAKOTA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

A TORNADO WATCH IS IN EFFECT UNTIL 1100 PM CDT. A FLASH FLOOD
WATCH IS IN EFFECT THROUGH SUNDAY AFTERNOON. THUNDERSTORMS WILL
DEVELOP ACROSS THE AREA THIS EVENING. ANY STORMS THAT DEVELOP ARE
LIKELY TO BECOME SEVERE...PRODUCING HEAVY RAIN...GUSTY WINDS AND
LARGE HAIL. AN ISOLATED TORNADO IS ALSO POSSIBLE.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THUNDERSTORMS ARE EXPECTED TO DEVELOP AGAIN ON SUNDAY. A FEW OF
THEM MAY PRODUCE GUSTY WINDS AND HAIL.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL LIKELY BE NEEDED THIS EVENING.

MNZ039-046-222100-
TRAVERSE-BIG STONE-
356 PM CDT SAT APR 21 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WEST CENTRAL
MINNESOTA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SHOWERS AND THUNDERSTORMS ARE POSSIBLE THIS EVENING. A FEW OF THE
STORMS MAY PRODUCE GUSTY WINDS AND HAIL.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THUNDERSTORMS ARE EXPECTED TO DEVELOP AGAIN ON SUNDAY. A FEW OF
THEM MAY PRODUCE GUSTY WINDS AND HAIL.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS EVENING.

SDZ004-009-020>023-222100-
CAMPBELL-WALWORTH-CODINGTON-GRANT-HAMLIN-DEUEL-
356 PM CDT SAT APR 21 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
SOUTH DAKOTA AND NORTHEAST SOUTH DAKOTA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

A TORNADO WATCH IS IN EFFECT UNTIL 1100 PM CDT. THUNDERSTORMS WILL
DEVELOP ACROSS THE AREA THIS EVENING. ANY STORMS THAT DEVELOP ARE
LIKELY TO BECOME SEVERE...PRODUCING GUSTY WINDS AND LARGE HAIL. AN
ISOLATED TORNADO IS ALSO POSSIBLE.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THUNDERSTORMS ARE EXPECTED TO DEVELOP AGAIN ON SUNDAY. A FEW OF
THEM MAY PRODUCE GUSTY WINDS AND HAIL.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL LIKELY BE NEEDED THIS EVENING.

PARKIN

The radar

The Aberdeen radar (KABR), 108 km away, was scanning. The volume nearest the first event began at 00:57 UTC.

Open the radar archive at this moment

Event by event

14 hail, 2 flash flood. Local standard time, as filed.

Hail, Clark

When: April 21, 6:55 PM CST
Where: Clark County, 4 mi W of Willow Lake
Measured: 0.88 in hail
Reported by: Trained Spotter
Coordinates: 44.630, -97.700

Hail, Clark

When: April 21, 6:58 PM CST
Where: Clark County, 5.1 mi WNW of Naples
Measured: 0.88 in hail
Reported by: Emergency Manager
Coordinates: 44.790, -97.600

Hail, Hamlin

When: April 21, 7:32 PM CST
Where: Hamlin County, 0.69 mi N of Hayti
Measured: 0.88 in hail
Reported by: Trained Spotter
Coordinates: 44.660, -97.200

Hail, Codington

When: April 21, 7:35 PM CST
Where: Codington County, 2.08 mi WSW of (Aty)watertown Arpt
Measured: 1 in hail
Reported by: Trained Spotter
Coordinates: 44.910, -97.190

Hail, Hamlin

When: April 21, 7:41 PM CST
Where: Hamlin County, 0.69 mi N of Hayti
Measured: 1 in hail
Reported by: Trained Spotter
Coordinates: 44.660, -97.200

Hail, Codington

When: April 21, 7:52 PM CST
Where: Codington County, 1.2 mi SW of (Aty)watertown Arpt
Measured: 1 in hail
Reported by: Trained Spotter
Coordinates: 44.910, -97.170

Hail, Hamlin

When: April 21, 7:53 PM CST
Where: Hamlin County, 1.63 mi ESE of Thomas
Measured: 1 in hail
Reported by: Trained Spotter
Coordinates: 44.760, -97.170

Hail, Codington

When: April 21, 7:58 PM CST
Where: Codington County, 1.2 mi SW of (Aty)watertown Arpt
Measured: 0.75 in hail
Reported by: Trained Spotter
Coordinates: 44.910, -97.170

Hail, Grant

When: April 21, 8:00 PM CST
Where: Grant County, 0.98 mi E of Stockholm
Measured: 0.75 in hail
Reported by: Trained Spotter
Coordinates: 45.100, -96.800

Hail, Grant

When: April 21, 8:05 PM CST
Where: Grant County, Milbank
Measured: 0.88 in hail
Reported by: Trained Spotter
Coordinates: 45.220, -96.630

Hail, Grant

When: April 21, 8:06 PM CST
Where: Grant County, 4.15 mi S of Milbank
Measured: 0.88 in hail
Reported by: Trained Spotter
Coordinates: 45.160, -96.630

Flash Flood, Codington

When: April 21, 8:10 PM CST to April 22, 2:00 AM CST
Where: Codington County, 1.2 mi SW of (Aty)watertown Arpt
Cause: Heavy Rain
Reported by: Emergency Manager
Coordinates: 44.910, -97.170

Heavy rains of 2 to 2.50 inches caused flash flooding in and around Watertown. Many streets were flooded in town along with several roads outside of town.

Hail, Codington

When: April 21, 8:10 PM CST
Where: Codington County, 1.2 mi SW of (Aty)watertown Arpt
Measured: 1 in hail
Reported by: Public
Coordinates: 44.910, -97.170

Hail, Grant

When: April 21, 8:20 PM CST
Where: Grant County, 2.08 mi S of Stockholm
Measured: 1 in hail
Reported by: Public
Coordinates: 45.070, -96.820

Hail, Hamlin

When: April 21, 9:24 PM CST
Where: Hamlin County, 2.95 mi E of Castlewood
Measured: 0.75 in hail
Reported by: Law Enforcement
Coordinates: 44.720, -96.970

Flash Flood, Hamlin

When: April 21, 11:58 PM CST to April 22, 2:30 AM CST
Where: Hamlin County, 0.85 mi SW of Thomas
Cause: Heavy Rain
Reported by: Trained Spotter
Coordinates: 44.760, -97.210

Heavy rains caused the flash flooding of several township roads near Thomas.

What these are

Hail: Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.
Flash Flood: Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in South Dakota in 2007 Every state in 2007 This day in weather history Warnings in South Dakota, April 2007

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 28588, 28589, 28590, 28591, 28592, 28593, 28594, 28595, 28596, 28597, 28598, 28586, 28599, 28600, 28602, 28587.