

881 

WWUS20 KWNS 162344

SEL2

SPC WW 162344

ILZ000-INZ000-LMZ000-170700-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 402

NWS STORM PREDICTION CENTER NORMAN OK

640 PM CDT SAT JUN 16 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHEAST ILLINOIS

       EXTREME NORTHWEST INDIANA

       LAKE MICHIGAN



EFFECTIVE THIS SATURDAY NIGHT AND SUNDAY MORNING FROM 640 PM

UNTIL 200 AM CDT.



HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 75

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



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 65

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 30 MILES WEST

NORTHWEST OF MARSEILLES ILLINOIS TO VALPARAISO INDIANA.  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 401...



DISCUSSION...EXPECT THE PROSPECT FOR SEVERE TSTMS TO INCRS ACROSS

NERN IL AND PARTS OF NW IND OVER THE NEXT SEVERAL HOURS. INITIAL

THREAT MAY EVOLVE FROM RECENT VIGOROUS DEVELOPMENT OCCURRING ALONG A

SW-NE ORIENTED THERMAL GRADIENT/WARM FRONT ACROSS NCNTRL TO NERN IL.

STORMS DEVELOPING ALONG THIS CORRIDOR MAY PRODUCE HAIL AND DOWNBURST

WINDS. MORE ORGANIZED DEVELOPMENT MAY EVOLVE THROUGH LATE EVENING AS

MCS SPREADS ENEWD INTO THE REGION FROM WATCH 401. THIS SYSTEM HAS A

WELL-DEFINED/MATURE COLD POOL AND IS ALSO ASSOCIATED WITH A BELT OF

STRONGER MID-LEVEL FLOW. STRENGTH OF THIS MCS WILL DEPEND SOMEWHAT

ON HOW MUCH PRIOR CONVECTIVE DEVELOPMENT OCCURS AHEAD OF IT.

HOWEVER...GIVEN THE COMBINED POTENTIAL FROM BOTH STORM

SCENARIOS...AND A CURRENTLY HOT AND WELL-MIXED BOUNDARY LAYER AWAY

FROM ONGOING CONVECTION...A WATCH ACROSS THE AREA SEEMS WARRANTED.



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

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 65

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

MOTION VECTOR 26035.





...CARBIN

