Name: Flash Flood in South Dakota, July 11, 2001
Start: 2001-07-11T16:45
End: 2001-07-11T18:20
Location: South Dakota

Where it happened

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

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 1

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 UNR wrote it up.

1.00 to over 2.50 inches of rain fell in about 3 hours over the Grizzly Creek basin. As the creek rose, debris blocked bridges forcing water over roadways. Several homes and businesses along the creek channel reported water in basements.

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 Rapid City, SD wrote its last area forecast discussion before the first event at Jul 11, 2:00 PM MST, 2 hours 45 minutes earlier.

Area forecast discussion, Jul 11, 2:00 PM MST, 2 hours 45 minutes before

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
300 PM MDT TUE JUL 10 2001

LATEST SFC ANALYSIS REVEALS LEE TROF EXTENDING FM NRN MT THROUGH ERN
WY. SFC LOW NOTED OVER SRN KS WITH A WARM FRONT EXTENDING N INTO SRN
NEB. SATELLITE IMAGES SHOW MID/HIGH CLOUDS LEFTOVER FROM LAST NIGHTS
CONVECTION OVER MUCH OF DAKOTAS. CU IS NOTED OVER AREAS OF WRN SD/SE
MT/NE WY WHERE SUNSHINE WASN'T BLOCKED. OROGRAPHIC INITIATED
CONVECTION NOTED ON AREA RADARS OVER BIG HORNS...BLACK HILLS AND
FRONT RANGE...APPEARS TO BE MOVING ONTO SURROUNDING PLAINS AND
DISSIPATING.

MODELS INITIALIZE WELL AND SHOW ABOUT AS GOOD AGREEMENT AS CAN BE
EXPECTED IN THIS PATTERN...NUMEROUS WEAK S/WVS MOVING IN SW FLOW
AROUND UPPER HIGH OVER TX. THIS RIDGE BUILDS A LITTLE INTO FRIDAY
OVER THE NORTHERN PLAINS...HOPEFULLY THIS WILL TAKE TRACK OF S/WV
ENERGY MORE N AND W OF CWFA. SOME MID LEVEL DRYING IS ANTICIPATED
THIS EVE...COMBINED WITH LOSS OF HEATING AND NO APPARENT VORT
MAX...ISOLD EARLY EVE CONVECTION CURRENTLY NOTED OVER WRN ZONES
SHOULD DIMINISH QUICKLY. WITH WEAK SHEAR PROFILES TODAY...DO NOT
ANTICIPATE SEVERE TSTMS. EXPECT ATMO TO REMAIN FAIRLY HOMOGENEOUS
OVER CWFA THROUGH THE EXTENDED. MOISTURE WILL REMAIN AVAILABLE AND
THE ATMO MILDLY UNSTABLE. WILL ANTICIPATE WEAK WAVES COOPERATING
WITH DAYTIME HEATING TO GET MAINLY OROGRAPHIC DIURNAL CONVECTION
GOING. R

GUIDANCE TEMPS LOOK GOOD. HAVE LEANED TO THE WARMER NGM NUMBERS.
POPS OVERDONE...ESPECIALLY EARLY PERIODS.
.UNR...NONE.

99

In the hours before

Local storm report, Jul 11, 4:34 PM MST, 11 minutes before

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The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

1 flash flood. Local standard time, as filed.

Flash Flood, Pennington

When: July 11, 4:45 PM MST to 6:20 PM MST
Where: Pennington County, Keystone
Reported by: EMERGENCY MANAGER
Coordinates: 44.004, -102.824 (the zone’s center; the record gives no point)

What these are

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

More

Every storm in South Dakota in 2001 Every state in 2001 This day in weather history Warnings in South Dakota, July 2001

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 2026-10-01. Each event’s entry at NCEI: 5260153.