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117 

WWUS20 KWNS 011347

SEL0

SPC WW 011347

NEZ000-SDZ000-012100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 240

NWS STORM PREDICTION CENTER NORMAN OK

850 AM CDT TUE JUN 1 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       LARGE PART OF EASTERN NEBRASKA

       PARTS OF SOUTHEASTERN SOUTH DAKOTA



EFFECTIVE THIS TUESDAY MORNING AND AFTERNOON FROM 850 AM UNTIL

400 PM CDT.



HAIL TO 2.5 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 100

STATUTE MILES EAST AND WEST OF A LINE FROM 80 MILES NORTHEAST OF

VALENTINE NEBRASKA TO 35 MILES SOUTHWEST OF BEATRICE NEBRASKA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU0).



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.



DISCUSSION...A VERY UNSTABLE AIR MASS HAS MOVED INTO THE WATCH AREA

OVERNIGHT ABOVE THE SURFACE WITH ELEVATED CAPES TO 3000 J/KG.  WITH

40-50 KT OF SHEAR ALONG WITH STEEP MID LEVEL LAPSE RATES...STORMS

WILL DEVELOP WITH LARGE HAIL PRIMARILY THE CONCERN.  WITH SURFACE

HEATING...POTENTIAL WILL INCREASE BY AFTERNOON FOR SUPERCELLS

INCREASING THE LARGE HAIL POTENTIAL FURTHER AS WELL AS THE DAMAGING

WIND THREAT.



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

TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

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

MOTION VECTOR 26030.





...HALES

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