

755 

WWUS20 KWNS 070215

SEL1

SPC WW 070215

NEZ000-SDZ000-071000-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 671

NWS STORM PREDICTION CENTER NORMAN OK

915 PM CDT THU AUG 6 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       PARTS OF WESTERN AND CENTRAL NEBRASKA

       SOUTH-CENTRAL SOUTH DAKOTA



EFFECTIVE THIS THURSDAY NIGHT AND FRIDAY MORNING FROM 915 PM

UNTIL 500 AM CDT.



HAIL TO 2 INCHES 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 65

STATUTE MILES EAST AND WEST OF A LINE FROM 60 MILES NORTH OF

VALENTINE NEBRASKA TO 45 MILES EAST SOUTHEAST OF IMPERIAL

NEBRASKA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).



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

TORNADO WATCH NUMBER 669. WATCH NUMBER 669 WILL NOT BE IN EFFECT

AFTER 915 PM CDT. CONTINUE...WW 667...WW 668...WW 670...



DISCUSSION...BROKEN BAND OF TSTMS ARE EXPECTED TO INTENSIFY TONIGHT

WHILE PROGRESSING EWD INTO A MOIST/UNSTABLE AIR MASS WHERE INFLOW

WILL BE ENHANCED BY 40-50 KT SLY LLJ.  THE COMBINATION OF THE

MODERATE INSTABILITY /MLCAPE OF 1000-1500 J PER KG/ AND AROUND 40 KT

OF DEEP WLY SHEAR WILL BE SUPPORTIVE OF EMBEDDED BOWING STRUCTURES

CAPABLE OF DAMAGING WINDS AND HAIL.



AVIATION...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 27030.





...MEAD/HALES

