

029 

WWUS20 KWNS 281302

SEL4

SPC WW 281302

IAZ000-MNZ000-NEZ000-SDZ000-281900-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 814

NWS STORM PREDICTION CENTER NORMAN OK

800 AM CDT SUN AUG 28 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       CENTRAL AND WESTERN IOWA

       EXTREME SOUTHWESTERN MINNESOTA

       EASTERN NEBRASKA

       SOUTHEASTERN SOUTH DAKOTA



EFFECTIVE THIS SUNDAY MORNING AND AFTERNOON FROM 800 AM UNTIL 200

PM CDT.



HAIL TO 2.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 75

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



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 85

STATUTE MILES EITHER SIDE OF A LINE FROM 55 MILES WEST NORTHWEST

OF SIOUX FALLS SOUTH DAKOTA TO 45 MILES EAST OF OMAHA NEBRASKA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU4).



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 813...



DISCUSSION...ERN SD MCS IS GROWING UPSCALE AND DEVELOPING COLD

POOL...WITH ORGANIZED CONVECTIVE WIND-DAMAGE THREAT INCREASING PER

MEASURED 48-KT GUST AT HON AT 1233Z.  POTENTIAL WILL CONTINUE FOR

DAMAGING GUSTS TO PENETRATE SHALLOW/NEAR-SFC STABLE LAYER...AS WELL

AS FOR LARGE HAIL WITH THIS AND FOREGOING CONVECTION...GIVEN

FAVORABLE ENVIRONMENTAL WIND AND BUOYANCY PROFILES.



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

TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 65

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

MOTION VECTOR 30035.





...EDWARDS

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