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931 

WWUS20 KWNS 220210

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SPC WW 220210

IAZ000-MNZ000-NEZ000-SDZ000-220900-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 341

NWS STORM PREDICTION CENTER NORMAN OK

910 PM CDT FRI JUN 21 2013



THE NWS STORM PREDICTION CENTER HAS ISSUED A



* SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

  NORTHWEST IOWA

  SOUTHWEST MINNESOTA

  NORTHEAST NEBRASKA

  SOUTHEAST SOUTH DAKOTA



* EFFECTIVE THIS FRIDAY NIGHT AND SATURDAY MORNING FROM 910 PM

  UNTIL 400 AM CDT.



* PRIMARY THREATS INCLUDE...

  SEVERAL LARGE HAIL EVENTS WITH A FEW VERY LARGE HAIL EVENTS TO

    2.5 INCHES IN DIAMETER POSSIBLE

  SEVERAL DAMAGING WIND GUSTS TO 70 MPH POSSIBLE



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 70

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 10 MILES NORTHWEST

OF AINSWORTH NEBRASKA TO 60 MILES EAST NORTHEAST OF SIOUX FALLS

SOUTH DAKOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).



PRECAUTIONARY/PREPAREDNESS ACTIONS...



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...THIS SEVERE THUNDERSTORM WATCH REPLACES

TORNADO WATCH NUMBER 336. WATCH NUMBER 336 WILL NOT BE IN EFFECT

AFTER 910 PM CDT. CONTINUE...WW 337...WW 338...WW 339...WW 340...



DISCUSSION...THUNDERSTORMS WERE INCREASING RAPIDLY ALONG SHARP

QUASI-STATIONARY FRONTAL ZONE BISECTING NEB FROM SW TO NE. THIS

DEVELOPMENT IS OCCURRING AMIDST A VERY UNSTABLE AIRMASS IN ONE OF

THE FEW REGIONS ACROSS THE CENTRAL PLAINS THAT HAS NOT SEEN

SIGNIFICANT CONVECTIVE OVERTURNING IN THE PAST 24H. DESPITE

RELATIVELY WARM TEMPERATURES ALOFT...IT APPEARS THAT NEAR SFC-BASED

PARCELS ARE ABLE TO OVERCOME INHIBITION AND SUPPORT CONTINUED STORM

DEVELOPMENT. IN ADDITION TO INCREASING MASS FLUX ACROSS THE FRONTAL

ZONE...LIFT OVER THE REGION MAY BE ENHANCED TONIGHT AS MCV/SHORT

WAVE TROUGH EMERGES EAST FROM HIGH PLAINS CONVECTION.

SHEAR/INSTABILITY WILL SUPPORT ORGANIZED/PERSISTENT UPDRAFTS CAPABLE

OF BOTH LARGE HAIL AND HIGH WINDS. SOME POTENTIAL WILL EXIST FOR

UPSCALE GROWTH AND MCS EVOLUTION THROUGH LATE TONIGHT/EARLY

SATURDAY.



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 26025.





...CARBIN

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