Tornado Watch 773

Issued

Jul 20, 2003, 2:50 PM CDT (19:50 UTC)

Expired

Jul 20, 2003, 9:00 PM CDT

In force

6 hr

Issued by

the Storm Prediction Center

The Omaha radar (KOAX), 98 km from the middle of the area, began a volume at 19:49 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.

• Mesoscale Discussion 1912Jul 20, 2:09 PM CDT
• Mesoscale Discussion 1918Jul 20, 5:29 PM CDT
• Mesoscale Discussion 1923Jul 20, 7:49 PM CDT
• Mesoscale Discussion 1924Jul 20, 8:08 PM CDT

000 
WWUS20 KWNS 201957
SEL3  
SPC WW 201950
IAZ000-NEZ000-SDZ000-210200-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 773 
NWS STORM PREDICTION CENTER NORMAN OK 
250 PM CDT SUN JUL 20 2003

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

       WESTERN IOWA
       EASTERN NEBRASKA
       EXTREME SOUTHEAST SOUTH DAKOTA

EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 250 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 80 STATUTE MILES EAST AND WEST
OF A LINE FROM 35 MILES EAST NORTHEAST OF YANKTON SOUTH DAKOTA TO
60 MILES WEST OF LAMONI IOWA.

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 771...WW 772...


DISCUSSION...EXTREME INSTABILITY HAS DEVELOPED NEAR AND W OF THE MO
RIVER WHERE MLCAPE VALUES NOW EXCEED 5000 J/KG.  SATELLITE IMAGERY
SHOWS A BAND OF APPARENT ACCAS OVER SE SD WHICH SIGNIFIES AT LEAST
WEAK ASCENT OVER THIS AREA. THUNDERSTORM DEVELOPMENT WILL BE
POSSIBLE IN THE NEXT 1-2 HOURS INVOF OF NE NEB/SE SD ALONG THE
INSTABILITY GRADIENT... WITH STORMS EXPECTED TO MOVE SE/SSEWD ALONG
THE MO RIVER VALLEY.  PARAMETERS APPEAR FAVORABLE FOR SUPERCELLS
WITH VERY LARGE HAIL AND DAMAGING WINDS.  ADDITIONALLY...BOUNDARY
LAYER DEW POINTS IN THE MID TO UPPER 70S AND ENHANCED LOW-LEVEL
SHEAR ALONG A REMNANT OUTFLOW BOUNDARY MAY BE SUFFICIENT FOR A
TORNADO THREAT.

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 650.
MEAN STORM MOTION VECTOR 32025.


...THOMPSON

430,0950 403,0933 403,0963 430,0981

Tornado Watches in Iowa, 2003Tornado Watches in Nebraska, 2003Tornado Watches in South Dakota, 2003Every tornado watch in 2003

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.