

000 

WWUS20 KWNS 050040

SEL4

SPC WW 050040

IAZ000-050400-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 564

NWS STORM PREDICTION CENTER NORMAN OK

740 PM CDT SAT AUG 4 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       NORTHWEST INTO CENTRAL IOWA



EFFECTIVE THIS SATURDAY EVENING FROM 740 PM UNTIL 1100 PM CDT.



TORNADOES...HAIL TO 2 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 60 STATUTE

MILES EAST AND WEST OF A LINE FROM 10 MILES NORTH OF STORM LAKE

IOWA TO 15 MILES EAST SOUTHEAST OF DES MOINES IOWA.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU4).



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 562...WW 563...



DISCUSSION...THUNDERSTORMS INCREASING OVER NWRN IA EARLY THIS

EVENING INVOF SURFACE LOW.  SHEAR REMAINS QUITE STRONG ACROSS THIS

REGION... ESPECIALLY SEWD ALONG WARM FRONT INTO CENTRAL IA.  GIVEN

PERSISTENT MODERATE TO STRONG INSTABILITY...STORMS SHOULD CONTINUE

MOVING SSEWD IN THE FORM OR DISCRETE SUPERCELLS THIS EVENING.

ENHANCED LOW LEVEL SHEAR AND VERY MOIST BOUNDARY LAYER WILL SUPPORT

A RISK OF TORNADOES INTO THIS AREA.



AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 2 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

500. MEAN STORM MOTION VECTOR 32020.





...EVANS

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