Alert archive / South Dakota / Tornado Watches in 1998

Tornado Watch 381

May 20, 1998Carter County, Montana; 10 counties in Nebraska; 11 counties in South Dakota

The Storm Prediction Center issued this tornado watch at May 20, 1998, 4:30 PM MDT for Carter County, Montana; 10 counties in Nebraska; 11 counties in South Dakota. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued: May 20, 1998, 4:30 PM MDT (22:30 UTC)
Expired: May 20, 1998, 11:00 PM MDT
In force: 7 hr
Issued by: the Storm Prediction Center

All 22 counties

Carter County, MT, Blaine County, NE, Brown County, NE, Cherry County, NE, Grant County, NE, Hooker County, NE, Logan County, NE, Loup County, NE, McPherson County, NE, Sheridan County, NE, Thomas County, NE, Bennett County, SD, Butte County, SD, Haakon County, SD, Jackson County, SD, Lawrence County, SD, Meade County, SD, Mellette County, SD, Oglala Lakota County, SD, Pennington County, SD, Perkins County, SD, Todd County, SD

The radar

The Rapid City radar (KUDX), 73 km from the middle of the area, began a volume at 22:32 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.

Warnings issued inside it

5 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
May 20, 4:40 PM MDT	Severe Thunderstorm Warning	UNR	Pennington	35 min
May 20, 5:23 PM MDT	Severe Thunderstorm Warning	UNR	Pennington	47 min
May 20, 6:13 PM MDT	Severe Thunderstorm Warning	UNR	Jackson, Pennington	32 min
May 20, 9:28 PM MDT	Severe Thunderstorm Warning	LBF	Cherry	62 min
May 20, 9:30 PM MDT	Severe Thunderstorm Warning	UNR	Todd	30 min

The nearest sounding before it

Aberdeen, SD (KABR), launched 12:00Z, 10.5 hours before the alert went out and 304 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1441 m above ground
0-6 km bulk shear: 27 kt
0-1 km storm-relative helicity: -85 m²/s²
0-3 km storm-relative helicity: 10 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

656 
WWUS9 KMKC 202155
SEL1  
MKC WW 202155
SDZ000-NEZ000-210500-

BULLETIN - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 381
STORM PREDICTION CENTER NORMAN OK
455 PM CDT WED MAY 20 1998

THE STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

   SOUTH DAKOTA                       
   NORTH CENTRAL NEBRASKA                           

EFFECTIVE THIS WEDNESDAY NIGHT AND THURSDAY MORNING FROM 530 PM
UNTIL MIDNIGHT CDT.

TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS ALONG AND 65 STATUTE MILES EAST AND WEST
OF A LINE FROM 20 MILES NORTH OF REDIG SOUTH DAKOTA TO 35 MILES
WEST OF BROKEN BOW NEBRASKA.

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA. 
PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING
WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS AND POSSIBLE
WARNINGS.

OTHER WATCH INFORMATION...  CONTINUE...WW 378...WW 379...WW 380...

DISCUSSION...THUNDERSTORMS SHOULD CONTINUE TO SPREAD FROM WY/NEB
PANHANDLE INTO SD AND NORTH CENTRAL NEB THIS EVENING. STRONG
DIRECTIONAL SHEAR WILL SUPPORT SUPERCELL DEVELOPMENT. ALTHOUGH THE
MAIN THREAT WILL BE FROM LARGE HAIL...BRIEF TORNADOES ARE POSSIBLE.


AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 2 INCHES.  EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 70 KNOTS.  A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. 
MEAN STORM MOTION VECTOR 24030.


...VESCIO

453,1021 412,0990 412,1013 453,1045

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 19, 6:00 PM MDT	Tornado Watch	SPC	Arthur, Blaine, Brown, Cherry, Custer, Grant and 9 more	5 hr
May 19, 9:00 PM MDT	Severe Thunderstorm Watch	SPC	Adams, Antelope, Blaine, Boone, Brown, Buffalo and 41 more	6 hr
May 20, 12:45 AM MDT	Severe Thunderstorm Watch	SPC	Burt, Cass, Cuming, Dodge, Douglas, Gage and 10 more	6 hr
May 20, 1:30 PM MDT	Tornado Watch	SPC	Arthur, Banner, Box Butte, Cheyenne, Dawes, Deuel and 6 more	6 hr

Nearby

Tornado Watches in South Dakota, 1998 Tornado Watches in Nebraska, 1998 Tornado Watches in Montana, 1998 Every tornado watch in 1998

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.