

944 

WWUS20 KWNS 092047

SEL6

SPC WW 092047

IAZ000-KSZ000-MOZ000-NEZ000-100400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 686

NWS STORM PREDICTION CENTER NORMAN OK

345 PM CDT SUN AUG 9 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHWEST AND CENTRAL IOWA

       NORTHEAST KANSAS

       NORTHWEST MISSOURI

       SOUTHEAST NEBRASKA



EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 345 PM UNTIL

1100 PM CDT.



HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80

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



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 55

STATUTE MILES EITHER SIDE OF A LINE FROM 50 MILES SOUTHWEST OF

BEATRICE NEBRASKA TO 50 MILES NORTH OF OTTUMWA IOWA.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU6).



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...CONTINUE...WW 682...WW 683...WW

684...WW 685...



DISCUSSION...INITIALLY ELEVATED CONVECTION IN A BAND FROM CENTRAL KS

INTO SWRN IA IS BEGINNING TO INTENSIFY BASED ON REMOTE SENSING DATA.

 ACTIVITY IS EXPECTED TO FURTHER INTENSIFY WITH INCREASING

LIKELIHOOD OF A FEW SURFACE-BASED STORMS DEVELOPING WITHIN VERY

UNSTABLE AIR MASS /MLCAPE 2000-3000 J PER KG/.  THE BAND IS ALONG

THE SERN EDGE OF STRONGER FLOW ALOFT WITH SUFFICIENT VERTICAL SHEAR

TO PROMOTE DEVELOPMENT OF SEVERE STORMS INCLUDING SUPERCELLS.

THREAT FOR DAMAGING WINDS AND LARGE HAIL WILL INCREASE THROUGH THE

EVENING HOURS AS ACTIVITY MOVES NEWD/ENEWD 30-35 KT.



AVIATION...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 550. MEAN STORM

MOTION VECTOR 24035.





...WEISS

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