

062 

WWUS20 KWNS 062210

SEL9

SPC WW 062210

NEZ000-SDZ000-070500-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 669

NWS STORM PREDICTION CENTER NORMAN OK

410 PM MDT THU AUG 6 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       PARTS OF WESTERN NEBRASKA AND THE PANHANDLE

       PARTS OF WESTERN AND SOUTH-CENTRAL SOUTH DAKOTA



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 410 PM UNTIL

1100 PM MDT.



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 70 STATUTE

MILES EAST AND WEST OF A LINE FROM 20 MILES EAST NORTHEAST OF

RAPID CITY SOUTH DAKOTA TO 20 MILES EAST SOUTHEAST OF SIDNEY

NEBRASKA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).



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 666...WW 667...WW 668...



DISCUSSION...TSTMS DEVELOPING OVER ERN WY AND THE NEB PNHDL ARE

EXPECTED TO INTENSIFY THIS EVENING WHILE PROGRESSING EWD INTO A

WARM/UNSTABLE AIR MASS WITH MLCAPE OF 1500-2500 J/KG.  REGIONAL VWPS

AND PROFILER DATA INDICATE THAT VERTICAL SHEAR IS ALREADY SUFFICIENT

FOR SUPERCELLS CAPABLE OF LARGE HAIL AND DAMAGING WINDS.  LOW-LEVEL

SHEAR IS FORECAST TO STEADILY INCREASE THIS EVENING IN CONJUNCTION

WITH STRENGTHENING LLJ...SUGGESTING A THREAT FOR TORNADOES.



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 28020.





...MEAD/HALES

