Alert archive / South Dakota / Flash Flood Warnings in 1999

Flash Flood Warning 16, NWS Sioux Falls, SD

July 20, 1999Yankton County, South Dakota

NWS Sioux Falls, SD issued this flash flood warning at Jul 20, 1999, 1:26 AM CDT for Yankton County, South Dakota. It was in force for 4 hr. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Jul 20, 1999, 1:26 AM CDT (06:26 UTC)
Expired: Jul 20, 1999, 5:25 AM CDT
In force: 4 hr
Issued by: NWS Sioux Falls, SD
Area: Whole counties

County Yankton County, SD

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 6.4 hours before the alert went out and 206 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 3192 J/kg
Mixed-layer CIN: -5 J/kg
Mixed-layer LCL: 1402 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 37 m²/s²
0-3 km storm-relative helicity: 91 m²/s²
Significant tornado parameter: 0.8
Supercell composite: 7.2

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

000 
TTAA00 KFSD 200627
FFWFSD
SDC027-127-135-201025-

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE SIOUX FALLS SD
126 AM CDT TUE JUL 20 1999

THE NATIONAL WEATHER SERVICE IN SIOUX FALLS HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  CLAY COUNTY IN SOUTHEASTERN SOUTH DAKOTA
  UNION COUNTY IN SOUTHEASTERN SOUTH DAKOTA
  YANKTON COUNTY IN SOUTHEASTERN SOUTH DAKOTA

* UNTIL 525 AM CDT

* AT 115 AM CDT... NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
  AN AREA OF THUNDERSTORMS WITH VERY HEAVY RAIN EXTENDING FROM
  THE LEWIS AND CLARK LAKE STATE RECREATION TO ELK POINT.  THESE
  STORMS WERE MOVING SLOWLY TO THE NORTHEAST.   LOCAL RAINFALL
  AMOUNTS IN EXCESS OF 2 INCHES AN HOUR ARE LIKELY THROUGH 4 AM.

BE ESPECIALLY CAUTIOUS AT NIGHT WHEN IT IS HARDER TO RECOGNIZE THE
DANGER OF FLOODING.

SCHUMACHER

What forecasters said that day

The local office's own words before this flash flood warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Sioux Falls, SD wrote its last area forecast discussion before this flash flood warning went out at Jul 19, 9:55 PM CDT, 3 hours 31 minutes earlier.

Area forecast discussion, Jul 19, 9:55 PM CDT, 3 hours 31 minutes before

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
955 PM CDT MON JUL 19 1999

NO SIGNIFICANT CHANGES TO BE MADE TO THE EARLIER FORECAST.  THE
FIRST ROUND OF THUNDERSTORMS WHICH DROPPED HEAVY RAINFALL IN
NORTHEAST NEBRASKA JUST SKIRTED THE SOUTHEAST PART OF THE CWA.
RECENT TRENDS OF SCATTERED THUNDERSTORMS HAVE TENDED TO DISSIPATE AS
THE REACH THE SD BORDER.  SO WILL WAIT FOR THE NEXT SIGNIFICANT
OPPORTUNITY FOR THUNDERSTORMS TO DEVELOP AS THE COMPLEX IN WESTERN
NE DEVELOPS NORTHEAST DURING THE NIGHT.  SLOW MOVING STORMS AND
ABUNDANT MOISTURE JUSTIFY KEEPING THE FLASH FLOOD WATCH ALONG THE
SOUTHERN SD BORDER AND INTO PART OF NORTHWEST IA AS ISSUED EARLIER.

.FSD...FFA TNGT                XTRM S CNTRL SD
       FFA TNGT AND TUE MRNG   XTRM SE SD/NERN NE/PARTS OF NW IA
 UMLAND

The office that day

Everything else NWS Sioux Falls, SD issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 20, 1:26 AM CDT	Flash Flood Warning	FSD	Clay, Union	4 hr
Jul 20, 1:48 AM CDT	Flash Flood Warning	FSD	Douglas	4 hr

Nearby

Flash Flood Warnings in South Dakota, 1999 Every flash flood warning in 1999

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive.