

671 

WWUS20 KWNS 072050

SEL2

SPC WW 072050

IAZ000-KSZ000-MOZ000-NEZ000-080400-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 342

NWS STORM PREDICTION CENTER NORMAN OK

350 PM CDT SUN JUN 7 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       SOUTHWEST IOWA

       NORTHEAST KANSAS

       NORTHWEST MISSOURI

       SOUTHEAST NEBRASKA



EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 350 PM UNTIL

1100 PM CDT.



TORNADOES...HAIL TO 3 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 90 STATUTE

MILES NORTH AND SOUTH OF A LINE FROM 35 MILES SOUTH SOUTHWEST OF

BEATRICE NEBRASKA TO 70 MILES NORTHEAST OF SAINT JOSEPH MISSOURI.

 FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU2).



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 341...



DISCUSSION...APPARENTLY SURFACE-BASED CONVECTION IS BEGINNING TO

DEVELOP ALONG THE SE NEB/NE KS BORDER IMMEDIATELY IN ADVANCE OF A

SURFACE WAVE ON THE FRONT...AND IN AN AREA OF STRONG INSTABILITY.

DESPITE THE WARMING NOTED IN THE 850-700 MB LAYER IN THE 19Z TOP AND

20Z VORTEX2 SPECIAL SOUNDING IN SE NEB...COOLING IS LIKELY OCCURRING

FROM THE W WITH THE CLOUD BAND AND AN ASSOCIATED SHORTWAVE TROUGH

EJECTING NEWD OVER CENTRAL KS.  GIVEN THIS EARLY

DEVELOPMENT...THUNDERSTORM COVERAGE WILL LIKELY INCREASE THROUGH THE

AFTERNOON/EVENING.  THE STORM ENVIRONMENT IS FAVORABLE FOR

SUPERCELLS WITH VERY LARGE HAIL GIVEN STEEP MID LEVEL LAPSE

RATES...MLCAPE OF 2500-3500 J/KG...AND STRONG DEEP LAYER VERTICAL

SHEAR.  ADDITIONALLY...BOUNDARY LAYER DEWPOINTS IN THE UPPER 60S AND

BACKING/STRENGTHENING LOW-LEVEL FLOW WILL CONTRIBUTE TO AN

INCREASINGLY FAVORABLE ENVIRONMENT FOR A FEW TORNADOES THROUGH LATE

EVENING.



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

SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE

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

550. MEAN STORM MOTION VECTOR 25030.





...THOMPSON

