

000 

WWUS20 KWNS 190340

SEL0

SPC WW 190340

IAZ000-NEZ000-191100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 540

NWS STORM PREDICTION CENTER NORMAN OK

1040 PM CDT WED JUL 18 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WESTERN AND CENTRAL IOWA

       EASTERN NEBRASKA



EFFECTIVE THIS WEDNESDAY NIGHT AND THURSDAY MORNING FROM 1040 PM

UNTIL 600 AM CDT.



HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 115

STATUTE MILES EAST AND WEST OF A LINE FROM 75 MILES NORTH

NORTHEAST OF DES MOINES IOWA TO 40 MILES EAST SOUTHEAST OF OMAHA

NEBRASKA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).



REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE

FAVORABLE FOR 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. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY

DO PRODUCE TORNADOES.



OTHER WATCH INFORMATION...THIS SEVERE THUNDERSTORM WATCH REPLACES

SEVERE THUNDERSTORM WATCH NUMBER 534. WATCH NUMBER 534 WILL NOT

BE IN EFFECT AFTER 1040 PM CDT. CONTINUE...WW 536...WW 537...WW

538...WW 539...



DISCUSSION...SLIGHTLY ELEVATED SUSTAINED STORMS/POSSIBLE SUPERCELLS

EXPECTED TO DEVELOP E/ESE INTO WW AS WAA/ASCENT CONTINUE TO INCREASE

INVOF STALLED FRONTAL ZONE/OUTFLOW BOUNDARY DOWNSTREAM FROM CNTRL

NEB MCS.  HIGH PWS...STEEP MID LVL LAPSE RATES AND MID LEVEL T/TD

SPREADS ALL SUGGEST POTENTIAL FOR SMALL SCALE BOWING SEGMENTS WITH

WET MICROBURSTS...IN ADDITION TO MARGINALLY SVR HAIL...THROUGH EARLY

THURSDAY.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS.

A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM MOTION

VECTOR 30025.





...CORFIDI

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