

589 

WWUS20 KWNS 192354

SEL3

SPC WW 192354

IAZ000-NEZ000-200700-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 283

NWS STORM PREDICTION CENTER NORMAN OK

655 PM CDT SAT MAY 19 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHWEST IOWA

       FAR NORTHEAST NEBRASKA



EFFECTIVE THIS SATURDAY NIGHT AND SUNDAY MORNING FROM 655 PM

UNTIL 200 AM CDT.



HAIL TO 2 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 60

STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES SOUTH OF

SIOUX CITY IOWA TO 30 MILES NORTHEAST OF SPENCER IOWA.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU3).



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 281...WW 282...



DISCUSSION...SEVERE TSTMS IN PROGRESS OVER ERN NEB ARE EXPECTED TO

MOVE/DEVELOP NEWD ACROSS THE WATCH AREA THIS EVENING INTO TONIGHT IN

ADVANCE OF MIDLEVEL VORTICITY MAXIMUM CURRENTLY OVER S-CNTRL NEB.

00Z OAX SOUNDING INDICATES THAT PRE-FRONTAL AIR MASS HAS BECOME

MODERATELY UNSTABLE OWING TO STEEP LAPSE RATES AND A RELATIVELY

MOIST BOUNDARY LAYER.  WHEN COUPLED WITH AROUND 40 KT OF DEEP SWLY

SHEAR...SETUP WILL SUPPORT POSSIBLE SUPERCELL STRUCTURES WITH A RISK

FOR LARGE HAIL AND DAMAGING WINDS.



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

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM

MOTION VECTOR 24025.





...MEAD

