Alert archive / South Dakota / Tornado Warnings in 2001

Tornado Warning 5, NWS Sioux Falls, SD

April 20, 2001Clay County, Union County, South Dakota; Dixon County, Nebraska

NWS Sioux Falls, SD issued this tornado warning at Apr 20, 2001, 9:04 PM CDT for Clay County, Union County, South Dakota; Dixon County, Nebraska. It was in force for 26 min. 2 reports came from inside the area while it was in force.

The area

The outline the Iowa Environmental Mesonet reconstructed for it; the warning itself named whole counties, with what was reported inside it.

The facts

Issued: Apr 20, 2001, 9:04 PM CDT (02:04 UTC)
Expired: Apr 20, 2001, 9:30 PM CDT
In force: 26 min
Issued by: NWS Sioux Falls, SD
Area: Whole counties; the outline is the Mesonet’s reconstruction

Counties Dixon County, NE, Clay County, SD, Union County, SD

The radar

The Sioux Falls radar (KFSD), 94 km from the middle of the area, began a volume at 02:06 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What was reported inside it

Time	Report	Where	Remark
Apr 20, 9:05 PM CDT	Hail 0.88	Newcastle, NE
Apr 20, 9:25 PM CDT	Hail 0.75	Spink, SD

NCEI Storm Data entries that began inside the alert's area while it was in force. Before 2003 the local storm report archive is thin, so this is the record of what happened rather than what was phoned in.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Apr 20, 8:15 PM CDT	Severe Thunderstorm Watch	SPC	6 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 2.1 hours before the alert went out and 163 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: 939 J/kg
Mixed-layer CIN: -84 J/kg
Mixed-layer LCL: 1568 m above ground
0-6 km bulk shear: 51 kt
0-1 km storm-relative helicity: 119 m²/s²
0-3 km storm-relative helicity: 247 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 4.8

Open this sounding in Storm Lab

The text

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

000 
WFUS53 KFSD 210204
TORFSD
NEC051-SDC027-127-210230-

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE SIOUX FALLS SD
904 PM CDT FRI APR 20 2001

THE NATIONAL WEATHER SERVICE IN SIOUX FALLS HAS ISSUED A

* TORNADO WARNING FOR...
  EXTREME NORTHERN DIXON COUNTY IN NORTHEAST NEBRASKA
  SOUTHEAST CLAY COUNTY IN SOUTHEAST SOUTH DAKOTA
  SOUTHERN UNION COUNTY IN SOUTHEAST SOUTH DAKOTA

* UNTIL 930 PM CDT

* AT 904 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  TORNADO OVER NEWCASTLE...OR ABOUT 8 MILES SOUTH OF VERMILLION...
  MOVING NORTHEAST AT 35 MPH.

* THE TORNADO WILL BE NEAR...
  BURBANK AROUND 915 PM CDT

THIS IS AN EXTREMELY DANGEROUS AND LIFE THREATENING SITUATION. TAKE
COVER NOW.

LAT...LON 4271 9704 4256 9690 4276 9664 4300 9653

The office that day

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

Issued	Product	Office	Counties	Lasted
Apr 20, 7:59 PM CDT	Severe Thunderstorm Warning	FSD	Union	31 min
Apr 20, 8:28 PM CDT	Severe Thunderstorm Warning	FSD	Clay, Union	32 min
Apr 20, 9:30 PM CDT	Tornado Warning	FSD	Union	30 min
Apr 21, 1:38 AM CDT	Severe Thunderstorm Warning	FSD	Clay	37 min
Apr 20, 7:19 PM CDT	Severe Thunderstorm Warning	FSD	Dakota, Dixon	26 min
Apr 20, 7:32 PM CDT	Tornado Warning	FSD	Dakota, Dixon	28 min
Apr 20, 10:32 PM CDT	Severe Thunderstorm Warning	FSD	Dakota	28 min

Nearby

Tornado Warnings in South Dakota, 2001 Tornado Warnings in Nebraska, 2001 Every tornado warning in 2001 Tornadoes in 2001

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; verification from NCEI's Storm Data; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.