Alert archive / Iowa / Severe Thunderstorm Warnings in 1997

Severe Thunderstorm Warning 36, NWS Sioux Falls, SD

June 20, 1997Plymouth County, Iowa; Union County, South Dakota

NWS Sioux Falls, SD issued this severe thunderstorm warning at Jun 20, 1997, 10:27 PM CDT for Plymouth County, Iowa; Union County, South Dakota. It was in force for 33 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Jun 20, 1997, 10:27 PM CDT (03:27 UTC)
Expired: Jun 20, 1997, 11:00 PM CDT
In force: 33 min
Issued by: NWS Sioux Falls, SD
Area: Whole counties

Counties Plymouth County, IA, Union County, SD

The radar

The Sioux Falls radar (KFSD), 92 km from the middle of the area, began a volume at 03:31 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.

The watch it was issued in

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

Issued	Product	Office	Lasted
Jun 20, 10:00 PM CDT	Severe Thunderstorm Watch	SPC	6 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 3.5 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: 5994 J/kg
Mixed-layer CIN: -4 J/kg
Mixed-layer LCL: 1151 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 89 m²/s²
0-3 km storm-relative helicity: 186 m²/s²
Significant tornado parameter: 4.8
Supercell composite: 25.7

Open this sounding in Storm Lab

The text

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

000 
TTAA00 KFSD 210327 RRA
SVRFSD
IAC149-SDC127-210400-

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1027 PM CDT FRI JUN 20 1997

* SEVERE THUNDERSTORM WARNING FOR
  SOUTHERN UNION COUNTY - IN SOUTHEASTERN SOUTH DAKOTA
  SOUTHWESTERN PLYMOUTH COUNTY - IN NORTHWESTERN IOWA

* UNTIL 1100 PM CDT
 
* SOME AREAS AFFECTED
  NORTH SIOUX CITY         AROUND 1030 PM CDT
  MC COOK LAKE             AROUND 1030 PM CDT
  JEFFERSON                AROUND 1035 PM CDT

* AT 1024 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
  A SEVERE THUNDERSTORM 11 MILES WEST OF SIOUX CITY  OR 4 MILES
  SOUTHWEST OF JEFFERSON MOVING NORTHEAST AT 30 MPH.
 
IF YOU ARE OUTDOORS...MOVE TO A PLACE OF SHELTER IMMEDIATELY IF A
STORM APPROACHES.  MOTORISTS SHOULD REMAIN ALERT FOR REDUCED
VISIBILITIES DURING DOWNPOURS OF RAIN.  STREETS MAY FLOOD QUICKLY.


HARMON

What forecasters said that day

The local office's own words before this severe thunderstorm 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 severe thunderstorm warning went out at Jun 20, 9:06 PM CDT, 1 hour 21 minutes earlier.

Area forecast discussion, Jun 20, 9:06 PM CDT, 1 hour 21 minutes before

SOUTH DAKOTA/NORTHWEST IOWA/SOUTHWEST MINNESOTA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
905 PM CDT FRI JUN 20 1997

GOING INTO SEVERE WEATHER MODE WITH AN ACTIVE WARNING.  NO SIGNIFICANT
UPDATE FOR THE CWA FROM EARLIER ZONE FORECASTS.

.FSD...NONE
UMLAND

The office that day

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

Issued	Product	Office	Counties	Lasted
Jun 20, 9:00 PM CDT	Severe Thunderstorm Warning	FSD	Woodbury	45 min
Jun 20, 9:38 PM CDT	Severe Thunderstorm Warning	FSD	Ida	47 min
Jun 20, 9:45 PM CDT	Severe Thunderstorm Warning	FSD	Woodbury	35 min
Jun 20, 10:34 PM CDT	Severe Thunderstorm Warning	FSD	Lyon	31 min
Jun 20, 11:02 PM CDT	Severe Thunderstorm Warning	FSD	Lyon	33 min

Nearby

Severe Thunderstorm Warnings in Iowa, 1997 Severe Thunderstorm Warnings in South Dakota, 1997 Every severe thunderstorm warning in 1997

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; radar from the NEXRAD Level II archive.