Tornado Watch 623

Issued

Aug 20, 2007, 3:49 PM CDT (20:49 UTC)

Expired

Aug 20, 2007, 9:30 PM CDT

In force

6 hr

Issued by

the Storm Prediction Center

Largest hail expected

3 in

Strongest gust expected

60 kt

The Grand Island radar (KUEX), 93 km from the middle of the area, began a volume at 20:51 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.

Two or more tornadoes

40%

One or more EF2 to EF5 tornadoes

20%

Ten or more severe wind reports

30%

One or more gusts of 65 knots or more

20%

Ten or more severe hail reports

30%

One or more hailstones of 2 inches or more

30%

Six or more combined severe hail and wind reports

70%

• Mesoscale Discussion 1818Aug 20, 3:03 PM CDT
• Mesoscale Discussion 1822Aug 20, 6:27 PM CDT
• Mesoscale Discussion 1824Aug 20, 7:35 PM CDT

000
WWUS20 KWNS 202053
SEL3  
SPC WW 202053
IAZ000-NEZ000-210300-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 623
NWS STORM PREDICTION CENTER NORMAN OK
350 PM CDT MON AUG 20 2007

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

       WEST CENTRAL AND SOUTHWEST IOWA
       CENTRAL AND EASTERN NEBRASKA

EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 350 PM UNTIL
1000 PM CDT.

TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 90 STATUTE
MILES EAST AND WEST OF A LINE FROM 55 MILES WEST SOUTHWEST OF
BEATRICE NEBRASKA TO 40 MILES NORTHEAST OF NORFOLK NEBRASKA.  FOR
A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU3).

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 621...WW 622...

DISCUSSION...THUNDERSTORMS ARE EXPECTED TO CONTINUE DEVELOPING
ALONG/EAST OF SURFACE TROUGH LINE MOVING EWD ACROSS CENTRAL
NEBRASKA.  AIR MASS EAST OF THE TROUGH LINE IS VERY MOIST WITH DEW
POINTS IN 70S CONTRIBUTING TO VERY UNSTABLE CONDITIONS WITH MLCAPE
OF 3000-4000 J/KG.  WIND PROFILES INCREASE AND VEER WITH HEIGHT IN
THE LOW-MID LEVELS RESULTING IN DEEP LAYER SHEAR 40-50 KT SUPPORTIVE
OF SUPERCELLS.  IN ADDITION...LOW LEVEL SRH OF 200-300 M2/S2
/ESPECIALLY OVER EXTREME ERN NEB/WRN IA WHERE WINDS REMAIN BACKED IN
ASSOCIATION WITH OLD OUTFLOW BNDRY/ AND LOW LCL HEIGHTS SUGGEST
INCREASED TORNADO POTENTIAL...WITH ADDITIONAL THREAT FOR VERY LARGE
HAIL AND DAMAGING WINDS.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
550. MEAN STORM MOTION VECTOR 26025.


...WEISS

Tornado Watches in Nebraska, 2007Tornado Watches in Iowa, 2007Every tornado watch in 2007

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.