Severe Thunderstorm Warning 25, NWS Chicago, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
645 PM CDT FRI MAY 9 2003

AVIATION DISCUSSION FOR 00Z TAFS

DRIER AIR RAPDILY MOVING INTO N IL SO BELIEVE TS NOW IN CENTRAL IL
WILL STAY THERE. SO TAFS DRY. COULD BE SOMETHING AT SUNRISE AND
MIDDAY TOMORROW DEPENDING ON WHICH MODEL LOOK AT BUT ALL VERY
NEBULOUS SO NOT CONFIDENT ENOUGH AT THIS T5IME TO CARRY A PROB
GROUP. BEST BET LOOKS LIKE LATE AFTERNOON WHEN MAJOR SVR WX EPISODE
EXPLODES OVER AREA.

GUSTY SW WINDS TO QUICKLY DIE THIS EVE AS MIXING ENDS AND GO
VARIABLE BY MIDNIGHT AS WEAK FRONT IN AREA. WINDS GO SE AHEAD OF
APPROACHING LOW TOMORROW AFTERNOON.

AF

DISCUSSION FOR 330PM ZONES...

WARM FRONT HAS MOVED NORTH OF THE AREA THIS AFTERNOON WITH WARM
MOIST AIRMASS BEGINNING TO MOVE NORTH IN TO THE FORECAST AREA
HELPING SET STAGE FOR MODERATE RISK OF SEVERE WEATHER SATURDAY
AFTERNOON AND EVENING.

WEATHER OF CONCERN TONIGHT WILL OCCUR AS SHORTWAVE MOVES THROUGH
UPPER FLOW AND ACROSS SOUTHERN PORTION OF AREA. QPF SUGGEST THERE
MAY BE SOME HEAVY RAIN ASSOCIATED BUT FOCUS REMAINS TO THE SOUTH OF
CWA.

THROUGH CHANCE OF TRW LINGERS INTO MORNING HOURS THERE SHOULD BE A
BRIEF BREAK BEFORE ATMOSPHERE GETS READY FOR AFTERNOON ACTIVITY.
SYSTEM APPEARS TO HAVE GOOD LARGE SCALE SUPPORT WITH SHARPENING
UPPER TROF OVER THE NORTHERN PLAINS AND DEEPEING SURFACE LOW OVER
MID MISSISSIPPI VALLEY. MODELS PLACE LOW VCNTY UIN AT 00Z. SURFACE
LOW MOVES TO NORTHEAST WITH COLD FRONT BEDING SWEPT ACROSS CWA.
THOUGH SOME THUNDERSTORMS WILL DEVELOP IN UNSTABLE AIMRASS DURING
AFTERNOON HEAVIER ACTIVITY SHOULD OCCUR AS LINE OF
THUNDERSTORMS/SQALL LINE DEVELOPS AHEAD OF FRONT DURING AFTERNOON
AND MOVES ACROSS AREA. ACTIVITY APPEARS TO BE CONFINED TO AFTERNOON
AND EVENING HOURS WITH THREAT DECREASING AFTER 06Z. CWA APPEARS IN
DRY SLOT OVERNIGHT INTO SUNDAY MORNING THEN WRAP AROUND BRINGS
LINGERING THREAT OF SHOWERS AS UPPER LOW IS SLOW TO MOVE OFF TO EAST.

.CHI..NONE

ILZ003>006-008-010>014-019-020>023-032-033-039-INZ001-002-010-011-
019-101100-

HAZARDOUS WEATHER OUTLOOK....UPDATED
NATIONAL WEATHER SERVICE CHICAGO IL
725 PM CDT FRI MAY 9 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL AND NORTHEAST
ILLINOIS...NORTHWEST INDIANA...AND THE ADJACENT WATERS OF LAKE
MICHIGAN.

.DAY ONE... TONIGHT

A SEVERE THUNDERSTORM WATCH IS IN EFFECT FOR BENTON COUNTY TIL 1100
PM TONIGHT. STORMS MOVING NORTHEAST FROM CENTRAL ILLINOIS WILL SLIP
NORTH OF INTERSTATE 74 AND MOVE IN AND AROUND BENTON COUNTY TONIGHT.

ELSEWHERE THERE IS REMAINS A SLIGHT RISK OF SEVERE THUNDERSTORMS
OVER THE OUTLOOK AREA OVERNIGHT. THUNDERSTORMS MAY DEVELOP IN OUR
WARM UNSTABLE AIRMASS AND SPREAD OVER THE ENTIRE OUTLOOK AREA. THE
MAIN THUNDERSTORM ACTIVITY HOWEVER SHOULD BE GENERALLY SOUTH OF
INTERSTATE 80. THE THREAT FROM THESE STORMS WILL BE LARGE HAIL
AND DAMAGING WINDS.

.DAYS TWO THROUGH SEVEN... SATURDAY THROUGH THURSDAY

THERE IS A MODERATE RISK OF SEVERE WEATHER SATURDAY.

A VERY STRONG SURFACE LOW WILL MOVE FROM EASTERN KANSAS TO WISCONSIN
AND DEEPEN RAPIDLY DURING THE DAY. WARM...HUMID...UNSTABLE AIR WILL
BE IN PLACE ACROSS NORTHERN ILLINOIS AND NORTHWEST INDIANA AS THE
LOW MOVES THROUGH THE AREA. A BAND OF SEVERE STORMS IS EXPECTED TO
DEVELOP DURING THE AFTERNOON ALONG A COLD FRONT ASSOCIATED WITH THE
SURFACE LOW IN WESTERN ILLINOIS AND MOVE RAPIDLY EAST ACROSS THE
OUTLOOK AREA FROM MID AFTERNOON THROUGH THE EVENING HOURS. THIS
SETUP FAVORS THE DEVELOPMENT OF A LINE OF THUNDERSTORMS WITH
WIDESPREAD DAMAGING WINDS AND HAIL. THE POSSIBILITY EXISTS THAT
CONDITIONS WILL BE SUFFICIENT FOR THE DEVELOPMENT OF SOME TORNADOES
ALSO.

THIS STORM SYSTEM IS POTENTIALLY VERY DANGEROUS. YOU SHOULD PREPARE
FOR SEVERE WEATHER ON SATURDAY AND HAVE YOUR EMERGENCY PLANS IN
MIND.

IN ADDITION TO THE SEVERE STORM POTENTIAL...FLOODING HAZARDS ARE
ALSO POSSIBLE FROM THE TORRENTIAL DOWNPOURS THAT WILL ACCOMPANY
THESE STRONG STORMS. THE RECENT RAINS HAVE CAUSED RIVERS ACROSS
NORTHEAST ILLINOIS AND NORTHWEST INDIANA TO SUFFER SIGNIFICANT
RISES. SOME OF THESE RIVERS ARE FORECAST TO RISE ABOVE FLOOD STAGE
SATURDAY AND SUNDAY...WITH MINOR TO MODERATE FLOODING EXPECTED.

THESE RECENT RAINS HAVE SATURATED SOILS IN MANY AREAS WITH GROUND
WATER. ADDITIONAL HEAVY RAINS WILL PROBABLY CAUSE LOCALIZED FLOODING
OF ROADWAYS AND THE USUAL LOW LYING FLOOD-PRONE AREAS.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE NEEDED ACROSS BENTON COUNTY THIS EVENING AND MAY BE
NEEDED IN THE REMAINING AREAS SOUTH OF INTERSTATE 80 AFTER
MIDNIGHT.  SPOTTERS WILL BE NEEDED  THROUGHOUT THE OUTLOOK AREA
SATURDAY AND SATURDAY NIGHT.

&&

           NWS CHICAGO WEBPAGE

    HTTP://WWW.CRH.NOAA.GOV/LOT (LOWER CASE)
OR  HTTP://WEATHER.NOAA.GOV/CHICAGO (LOWER CASE)

RLB

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO IL
1100 PM CDT FRI MAY 09 2003

TIME(CDT)  .....CITY LOCATION..... STATE  ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0945 PM    BONFIELD                  IL   .75 INCH HAIL
05/09/03   KANKAKEE                       REPORTED BY COOPERATIVE
                                          OBSERVER.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO IL
1126 PM CDT FRI MAY 09 2003

TIME(CDT)  .....CITY LOCATION..... STATE  ...EVENT/REMARKS...
           ....COUNTY LOCATION....

1118 PM    ST CHARLES                IL   1.75 INCH HAIL
05/09/03   KANE                           KIRK AND NORTH AVENUE

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO IL
1130 PM CDT FRI MAY 09 2003

TIME(CDT)  .....CITY LOCATION..... STATE  ...EVENT/REMARKS...
           ....COUNTY LOCATION....

1118 PM    BATAVIA                   IL   1.25 INCH HAIL
05/09/03   KANE                           ORCHARD RH AND I88.
                                          REPORTED BY LAW
                                          ENFORCEMENT OFFICIAL.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHICAGO IL
1134 PM CDT FRI MAY 09 2003

TIME(CDT)  .....CITY LOCATION..... STATE  ...EVENT/REMARKS...
           ....COUNTY LOCATION....

1129 PM    ST CHARLES                IL   1 INCH HAIL
05/09/03   KANE                           REPORTED BY OFF-DUTY
                                          NWS EMPLOYEE.