Lightning Strike in Illinois, July 3, 2003

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
1245 PM CDT THU JUL 3 2003

UPDATED ZFP/GRIDS TO BUMP MAX TEMPS A LITTLE...AND TO LOWER POPS FOR
AFTERNOON THUNDERSTORMS. MCS REMNANTS QUICKLY DISSIPATED AS THEY
MOVED INTO FAR NW CWA THIS MORNING...AS THEY MOVED INTO AREA OF
STRONGER CAPPING AND SOMEWHAT LOWER INSTABILITY. SOME REFLECTION OF
OUTFLOW BOUNDARY SEEN IN EARLY MORNING SFC ANALYSIS...THOUGH LATER
OBS AND VIS SATELLITE PICS INDICATE THAT THIS FEATURE IS VERY
DIFFICULT TO LOCATE. MORE SIGNIFICANT OUTFLOW BOUNDARY NOTED FROM
LSE-VOK-OSH IN WI WITH DENSE CU BEGINNING TO FORM THERE. THEREFORE
LITTLE LOW LEVEL MOISTURE CONVERGENCE NOTED AT THE SURFACE IN WFO
CHI CWA TO INITIATE NEW DEVELOPMENT ON THIS AFTERNOON. THAT BEING
SAID...SURFACE DEWPOINTS INCREASING TO AROUND 70 DEG AND TEMPS
RISING INTO 90-92 RANGE THIS AFTERNOON WILL PROMOTE UNSTABLE
CONDITIONS WITH SBCAPES NEARING 3000 J/KG THIS AFTN...WITH SHORT
WAVE TROUGH AXIS PASSING THROUGH ALOFT. THUS HAVE REDUCED MENTION TO
ISOLATED AFTN TSTMS AND LOWERED POP TO 30 PCNT. SPC STILL HAS AREA
OUTLOOKED IN SLGT RISK...WITH SUFFICIENT SHEAR AND INSTABILITY TO
PRODUCE SVR CELLS IF ANY CAN INITIATE.

.CHI...NONE

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AVIATION DISCUSSION FOR 18Z TAFS:

MAIN FCST PROBLEM THIS FCST PERIOD CONCERNS TIMING OF TSTM DVLPMT.
WITH SFC TEMPS RISING INTO LOER 90S AND DEW POINTS IN 70S...AMS HAS
BECOME QUITE UNSTABLE...ALTHO CURRENT ACARS SOUNDINGS SHOW DISTINCT
MID LVL THERMAL CAP.  PRES INDICATIONS ARE THAT AFTN TSTM INITIATION
SHUD TAKE PLACE TO N AND W...BASED ON LATEST VIS SATLT TRENDS.  BAND
OF TCU FROM E CNTRL WI INVOF OSH...WSWWD TO NR LNR-DEH/RST AREA
APPEARS READY TO FIRE. EXPECT TSTM CLUSTER TO FORM IN THIS AREA AND
SLOLY PROPAGATE SWD INTO MOIST UNSTBL AMS OVR IA/SRN WI AND PERHAPS
NRN IL AFT 00Z. THIS ACTIVITY CURRENTLY FCST TO MOVE THRU TERMINAL
AREA OVERNIGHT INTO ERLY FRI...THEN A LULL BEFORE POTENTIALLY SVR
STMS MOVE IN FRI AFTN.   WITH THIS SCENARIO...WILL HAVE GENLY VFR
CONDS XCP MVFR VIS IN TSTMS.  BASED ON UNCERTAINTY IN TIMING WILL
JUST GO WITH PROB GROUP OVRNGT.  HOPEFULLY NEXT FEW HRS WILL SHED A
LTL MORE PRECISION ON TIMING AND CERTAINTY.  WIND TO BE GENLY FROM
SW WITH GUSTS AOA 20 KTS DURING THE HEAT OF THE AFTN.  WIND TO BCM
SSWLY DURG THIS EVE WITH SPEEDS DCRSG TO UNDER 10 KTS BY
SS.

MERZLOCK

ILZ003>006-008-010>014-019-020>023-032-033-039-
INZ001-002-010-011-019-031700-

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE CHICAGO IL
135 PM CDT THU JUL 3 2003

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

.DAY ONE... THIS AFTERNOON AND TONIGHT

THERE IS A SLIGHT CHANCE OF THUNDERSTORMS LATE THIS AFTERNOON
THROUGH THIS EVENING...ALTHOUGH THUNDERSTORMS ARE MORE LIKELY TO
REMAIN ACROSS WISCONSIN...CENTRAL LAKE MICHIGAN...AND LOWER
MICHIGAN. THERE IS A SLIGHT RISK OF THESE THUNDERSTORMS BECOMING
SEVERE...WITH DAMAGING WINDS AND LARGE HAIL.

.DAYS TWO THROUGH SEVEN... FRIDAY THROUGH WEDNESDAY

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ON FRIDAY...WITH
THE MAIN RISKS BEING SIGNIFICANT DAMAGING STRAIGHT LINE WINDS AND
LARGE HAIL. SEVERE THUNDERSTORMS WOULD BE MOST LIKELY TO AFFECT
WESTERN PORTIONS OF THE OUTLOOK AREA...WEST OF INTERSTATE 39...BY
MID TO LATE AFTERNOON...THE CHICAGO AND ILLINOIS RIVER VALLEY AREAS
BY LATE AFTERNOON OR EARLY EVENING...AND NORTHWEST INDIANA BY
EVENING.

A VERY MOIST AND UNSTABLE AIR MASS WILL BE IN PLACE ACROSS THE
OUTLOOK AREA ON FRIDAY. THUNDERSTORMS ARE EXPECTED TO INITIATE OVER
THE CENTRAL PLAINS LATE TONIGHT...DEVELOPING INTO A SIGNIFICANT
DAMAGING WIND PRODUCING THUNDERSTORM COMPLEX WHICH IS EXPECTED TO
MOVE EAST INTO UNSTABLE AIRMASS OVER THE GREAT LAKES REGION FRIDAY.

THERE IS A CHANCE OF THUNDERSTORMS AGAIN FROM LATE SUNDAY THROUGH
WEDNESDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS WILL NOT BE NEEDED TODAY OR TONIGHT.

&&

           NWS CHICAGO WEBPAGE

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

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