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Severe Thunderstorm Watch

SEVERE THUNDERSTORM WATCH OUTLINE UPDATE FOR WS 300
NWS STORM PREDICTION CENTER NORMAN OK
400 PM CDT WED JUN 12 2013

SEVERE THUNDERSTORM WATCH 300 IS IN EFFECT UNTIL 100 AM CDT
FOR THE FOLLOWING LOCATIONS

ILC031-043-053-075-091-097-197-130600-
/O.NEW.KWNS.SV.A.0300.130612T2100Z-130613T0600Z/

IL
. ILLINOIS COUNTIES INCLUDED ARE

COOK DUPAGE FORD
IROQUOIS KANKAKEE LAKE
WILL



________________________________________

Hazardous Weather Outlook

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
344 PM CDT WED JUN 12 2013

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
132045-
WINNEBAGO-BOONE-MCHENRY-LAKE ILLINOIS-OGLE-LEE-DE KALB-KANE-
DUPAGE-COOK-LA SALLE-KENDALL-GRUNDY-WILL-KANKAKEE-LIVINGSTON-
IROQUOIS-FORD-LAKE INDIANA-PORTER-NEWTON-JASPER-BENTON-
344 PM CDT WED JUN 12 2013 /444 PM EDT WED JUN 12 2013/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL ILLINOIS...
NORTHEAST ILLINOIS AND NORTHWEST INDIANA.

.DAY ONE...TONIGHT.

WEATHER HAZARDS EXPECTED:

NUMEROUS SEVERE THUNDERSTORMS...SOME COULD PRODUCE:

STRONG TORNADOES.
DAMAGING WINDS UP TO 80 TO 100 MPH.
ISOLATED HAIL TO THE SIZE OF BASEBALLS.
VERY HEAVY RAINFALL WHICH COULD CAUSE FLASH FLOODING

AREAS AFFECTED AND TIMING:

SCATTERED THUNDERSTORMS DEVELOPING ACROSS FAR EASTERN IOWA...
SOUTHWEST WISCONSIN...AND NORTHWEST ILLINOIS THIS AFTERNOON WILL EVOLVE EAST ACROSS NORTH CENTRAL ILLINOIS...INCLUDING THE ROCKFORD AREA...BY LATE AFTERNOON. THESE STORMS WILL HAVE AN ENHANCED TORNADIC THREAT AS THEY RAPIDLY STRENGTHEN INTO EARLY THIS EVENING. THE STORMS WILL MOVE EAST ACROSS ALL OF NORTHERN ILLINOIS AND INTO NORTHWEST INDIANA THROUGH THE EVENING HOURS.
THE STRONGEST THUNDERSTORMS WITH THE GREATEST PROBABILITY TO PRODUCE SEVERE WEATHER WILL IMPACT THE CHICAGOLAND AREA BETWEEN 6 AND 11 PM. THE PRIMARY THREAT OF THESE STORMS WILL BE DAMAGING
WINDS AND HEAVY RAINFALL...WITH ISOLATED THREATS OF LARGE HAIL AND TORNADOES. WHILE ALL STORMS WILL BE CAPABLE OF PRODUCING HEAVY RAIN...THE GREATEST FLASH FLOOD THREAT WILL LIKELY BE GENERALLY ALONG AND NORTH OF THE I-80 CORRIDOR IN NORTHERN ILLINOIS AND NORTH OF THE KANKAKEE RIVER IN NORTHWESTERN INDIANA...WHICH INCLUDES ALL OF THE CHICAGO AND ROCKFORD METRO AREAS.

DISCUSSION:

LOW PRESSURE WILL MOVE EAST ALONG A WARM FRONT ACROSS NORTHERN ILLINOIS AND INDIANA THIS EVENING. A VERY WARM...HUMID AND UNSTABLE AIR MASS WILL BE IN PLACE ALONG AND SOUTH OF THE WARM FRONT. THE COMBINATION OF STRONG INSTABILITY AND STRENGTHENING
WIND SHEAR WILL LIKELY LEAD TO A SIGNIFICANT SEVERE WEATHER OUTBREAK THROUGH THIS EVENING ACROSS THE REGION. STRONG...DAMAGING WIND IS THE GREATEST THREAT...BUT VERY LARGE HAIL AND ISOLATED TORNADOES ARE POSSIBLE AS WELL. IN ADDITION... HEAVY RAINFALL...MAINLY ALONG AND NORTH OF THE I-80 CORRIDOR IN ILLINOIS AND NORTH OF THE KANKAKEE RIVER IN INDIANA WILL LEAD TO THE POTENTIAL FOR FLASH FLOODING THROUGH TONIGHT.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

THERE IS AN INCREASED RISK FOR RIP CURRENTS THURSDAY.

THERE IS A CHANCE OF THUNDERSTORMS EARLY SATURDAY MORNING THROUGH
MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL BE NECESSARY THROUGH TONIGHT.