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WWUS20 KWNS 052349

SEL2

SPC WW 052349

IAZ000-MNZ000-NEZ000-SDZ000-060600-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 252

NWS STORM PREDICTION CENTER NORMAN OK

645 PM CDT SAT MAY 5 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       EXTREME NORTHWEST IOWA

       EXTREME SOUTHWEST MINNESOTA

       CENTRAL AND NORTH CENTRAL NEBRASKA

       SOUTHEAST SOUTH DAKOTA



EFFECTIVE THIS SATURDAY NIGHT AND SUNDAY MORNING FROM 645 PM

UNTIL 100 AM 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 45

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 85 MILES WEST

SOUTHWEST OF MULLEN NEBRASKA TO 35 MILES EAST SOUTHEAST OF

BROOKINGS SOUTH DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH

SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU2).



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 249...WW 250...WW 251...



DISCUSSION...ELEVATED THUNDERSTORMS WILL LIKELY INCREASE IN

COVERAGE/INTENSITY THROUGH EARLY TONIGHT IN A ZONE OF INCREASING WAA

FROM NRN NEB INTO SE SD.  STRONG INSTABILITY IS PRESENT ABOVE THE

FRONTAL SURFACE...AND STRONG CLOUD-LAYER SHEAR WILL SUPPORT A RISK

FOR ELEVATED SUPERCELLS CAPABLE OF PRODUCING VERY LARGE HAIL.  THE

RISK SHOULD INITIALLY BE CONFINED TO LARGE HAIL...THOUGH THERE WILL

BE SOME RISK FOR ISOLATED DAMAGING WINDS LATER AS STORM COVERAGE AND

COLD POOL PRODUCTION INCREASES.  FARTHER W...SUPERCELLS IN THE

POST-FRONTAL UPSLOPE REGIME IN THE SW NEB PANHANDLE COULD PROGRESS

FAR ENOUGH E TO IMPACT MORE OF SW NEB...BEFORE WEAKENING LATE THIS

EVENING.



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 500. MEAN STORM

MOTION VECTOR 24030.





...THOMPSON

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