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WWUS20 KWNS 241722

SEL3

SPC WW 241722

NEZ000-SDZ000-WYZ000-250200-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 213

NWS STORM PREDICTION CENTER NORMAN OK

1120 AM MDT MON MAY 24 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       WESTERN NEBRASKA

       WESTERN AND CENTRAL SOUTH DAKOTA

       EXTREME SOUTHEAST WYOMING



EFFECTIVE THIS MONDAY MORNING AND EVENING FROM 1120 AM UNTIL 800

PM MDT.



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 85 STATUTE

MILES EAST AND WEST OF A LINE FROM 30 MILES NORTH NORTHWEST OF

MOBRIDGE SOUTH DAKOTA TO 15 MILES EAST SOUTHEAST OF SIDNEY

NEBRASKA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).



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 212...



DISCUSSION...THUNDERSTORM DEVELOPMENT IS JUST BEGINNING ACROSS

EXTREME NE CO/SE WY AND THE NEB PANHANDLE.  THIS CONVECTION WILL

LIKELY EVOLVE INTO DISCRETE SUPERCELLS IN AN ENVIRONMENT OF STRONG

VERTICAL SHEAR AND MODERATE INSTABILITY...IN ADVANCE OF A NEGATIVE

TILT SHORTWAVE TROUGH AND SURFACE LOW MOVING NNEWD FROM CO.  THE

COMBINATION OF BOUNDARY LAYER DEWPOINTS IN THE MID 60S AND ENHANCED

LOW-LEVEL SHEAR NEAR THE SURFACE WARM FRONT WILL ENHANCE THE THREAT

FOR TORNADOES...INCLUDING AN ISOLATED STRONG TORNADO OR TWO...AS

WELL AS VERY LARGE HAIL.  OTHERWISE...CONVECTION MAY EVOLVE MORE

INTO CLUSTERS WITH EMBEDDED SUPERCELL STRUCTURES BY LATE

AFTERNOON...WITH THE ADDITIONAL THREAT OF DAMAGING WINDS.



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

500. MEAN STORM MOTION VECTOR 20045.





...THOMPSON

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