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WWUS20 KWNS 202225

SEL1

SPC WW 202225

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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 711

NWS STORM PREDICTION CENTER NORMAN OK

420 PM MDT SUN JUL 20 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHERN AND WESTERN NEBRASKA INCLUDING MUCH OF THE PANHANDLE

       SOUTHERN AND WESTERN SOUTH DAKOTA



EFFECTIVE THIS SUNDAY AFTERNOON FROM 420 PM UNTIL MIDNIGHT MDT.



HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 70

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 50 MILES WEST OF

CHADRON NEBRASKA TO 35 MILES EAST OF AINSWORTH 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...CONTINUE...WW 708...WW 709...WW 710...



DISCUSSION...THUNDERSTORMS EXPECTED TO INCREASE RAPIDLY LATE TODAY

OVER THE REGION AHEAD OF SHORTWAVE TROUGH MOVING ACROSS THE NRN HIGH

PLAINS AND NEAR SURFACE FRONT EXTENDING WNW OVER THE AREA.  CAP WILL

CONTINUE TO WEAKEN AND ALLOW PARCELS TO TAP EXTREME INSTABILITY AS

ACTIVITY EVOLVES EWD THROUGH THE EVENING.  DEEP LAYER SHEAR WILL BE

QUITE STRONG AND SUPPORT SUPERCELLS...ESPECIALLY WITH INITIAL

DEVELOPMENT.  HOWEVER...ACTIVITY IS EXPECTED TO EVOLVE INTO A LARGER

CLUSTER/LINE DURING THE EVENING AND RACE ESEWD ALONG AND JUST NORTH

OF THE BOUNDARY.  VERY LARGE HAIL AND STRONG/DAMAGING WINDS ARE

EXPECTED WITHIN WATCH AREA.  IF STORMS MAINTAIN DISCRETE NATURE NEAR

THE FRONT OVER CENTRAL NEB WHERE MOISTURE REMAINS GREATER...

POTENTIAL FOR A FEW TORNADOES MAY INCREASE AND REQUIRE PARTIAL WATCH

UPGRADE LATER THIS EVENING.



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

TO 3 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70

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

MOTION VECTOR 27035.





...EVANS

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