Alert archive / South Dakota / Tornado Watches in 2004
Tornado Watch 657
The Storm Prediction Center issued this tornado watch at Jul 20, 2004, 2:40 PM CDT for 15 counties in Nebraska; 26 counties in South Dakota. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 20, 2004, 2:40 PM CDT (19:40 UTC)
- Expired
- Jul 20, 2004, 9:00 PM CDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
All 41 counties
Antelope County, NE, Boyd County, NE, Cedar County, NE, Cuming County, NE, Dixon County, NE, Garfield County, NE, Holt County, NE, Knox County, NE, Loup County, NE, Madison County, NE, Pierce County, NE, Rock County, NE, Stanton County, NE, Wayne County, NE, Wheeler County, NE, Aurora County, SD, Beadle County, SD, Bon Homme County, SD, Brookings County, SD, Brule County, SD, Buffalo County, SD, Charles Mix County, SD, Clay County, SD, Davison County, SD, Douglas County, SD, Gregory County, SD, Hand County, SD, Hanson County, SD, Hutchinson County, SD, Jerauld County, SD, Kingsbury County, SD, Lake County, SD, Lincoln County, SD, McCook County, SD, Miner County, SD, Minnehaha County, SD, Moody County, SD, Sanborn County, SD, Turner County, SD, Union County, SD, Yankton County, SD
The radar
The Sioux Falls radar (KFSD), 150 km from the middle of the area, began a volume at 19:43 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
14 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 20, 4:44 PM CDT | Severe Thunderstorm Warning | LBF | Garfield, Loup | 61 min |
| Jul 20, 4:58 PM CDT | Severe Thunderstorm Warning | LBF | Holt | 62 min |
| Jul 20, 5:55 PM CDT | Severe Thunderstorm Warning | LBF | Boyd | 50 min |
| Jul 20, 6:02 PM CDT | Severe Thunderstorm Warning | FSD | Davison | 28 min |
| Jul 20, 6:25 PM CDT | Severe Thunderstorm Warning | FSD | Douglas | 35 min |
| Jul 20, 6:28 PM CDT | Severe Thunderstorm Warning | FSD | Davison | 32 min |
| Jul 20, 6:41 PM CDT | Severe Thunderstorm Warning | FSD | Hanson | 34 min |
| Jul 20, 6:58 PM CDT | Severe Thunderstorm Warning | FSD | Davison, Douglas | 32 min |
| Jul 20, 7:14 PM CDT | Severe Thunderstorm Warning | FSD | Hanson | 31 min |
| Jul 20, 7:29 PM CDT | Severe Thunderstorm Warning | FSD | Davison, Douglas, Hutchinson | 31 min |
| Jul 20, 7:33 PM CDT | Severe Thunderstorm Warning | FSD | McCook, Miner | 42 min |
| Jul 20, 8:10 PM CDT | Severe Thunderstorm Warning | FSD | Lake | 35 min |
| Jul 20, 8:27 PM CDT | Severe Thunderstorm Warning | FSD | Moody | 33 min |
| Jul 20, 8:59 PM CDT | Severe Thunderstorm Warning | FSD | Moody | 31 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Aberdeen, SD (KABR), launched 12:00Z, 7.7 hours before the alert went out and 221 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.
- Mixed-layer CAPE
- 16 J/kg
- Mixed-layer CIN
- -354 J/kg
- Mixed-layer LCL
- 1535 m above ground
- 0-6 km bulk shear
- 14 kt
- 0-1 km storm-relative helicity
- 6 m²/s²
- 0-3 km storm-relative helicity
- 127 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
000
WWUS20 KWNS 201940
SEL7
SPC WW 201940
NEZ000-SDZ000-210200-
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 657
NWS STORM PREDICTION CENTER NORMAN OK
240 PM CDT TUE JUL 20 2004
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
NORTHEAST NEBRASKA
SOUTHEAST SOUTH DAKOTA
EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 240 PM UNTIL 900
PM CDT.
TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.
THE TORNADO WATCH AREA IS ALONG AND 75 STATUTE MILES EAST AND WEST
OF A LINE FROM 25 MILES NORTHEAST OF HURON SOUTH DAKOTA TO 40
MILES WEST SOUTHWEST OF NORFOLK 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.
DISCUSSION...VERY UNSTABLE AIR MASS IN PLACE ACROSS WATCH AREA WITH
CAP BECOMING VERY WEAK WRN PORTION. RAPID DEVELOPMENT OF SEVERE
THUNDERSTORMS EXPECTED IN AREA OF BEST LOW LVL CONVERGENCE VICINITY
NEB/SD BORDER W OF YKN. VEERING SHEAR PROFILES SUPPORT SUPERCELLS
WHICH WILL ENHANCE POTENTIAL FOR VERY LARGE HAIL AND ISOLATED
TORNADOES.
AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 600.
MEAN STORM MOTION VECTOR 27025.
...HALES
443,0961 414,0964 414,0993 443,0992SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 20, 2:16 PM CDT | Mesoscale Discussion | SPC | Antelope, Boone, Boyd, Burt, Cedar, Colfax and 17 more | 119 min |
| Jul 20, 6:30 PM CDT | Mesoscale Discussion | SPC | Antelope, Boyd, Cedar, Dixon, Holt, Knox and 4 more | 90 min |
| Jul 20, 3:28 PM CDT | Mesoscale Discussion | SPC | Campbell, Corson, Dewey, Harding, Perkins, Potter and 2 more | 2 hr |
| Jul 20, 3:55 PM CDT | Severe Thunderstorm Watch | SPC | Campbell, Corson, Dewey, Harding, McPherson, Perkins and 3 more | 6 hr |
Nearby
Tornado Watches in South Dakota, 2004Tornado Watches in Nebraska, 2004Every tornado watch in 2004
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.