Tornado Warning 46, NWS Chicago, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
330 PM CDT THU JUN 10 2004

.DISCUSSION FOR AFTERNOON ZONES/GRIDS...
FCST FOCUS ON SHORT TERM WITH TSRA DVLPMNT TNGT AND POTENTIAL HVY RA
AND RESULTING FLOODING. SFC BNDRY JUST N OF VPZ TO DPA TO JUST N OF
DBQ...AND HAS MOVD LTL DURG DAY. AREA OF MAINLY -RA CONTS TO SLOLY
NEWRD THRU NRN IL INTO SRR WI AS SHORT WAV SHEARS NE INTO UPR RDG.
HEAVIER RA THIS A.M. PUT DOWN UP TO 2 INCHES ACROSS EXTREME NERN IL.
TSRA CONT TO DVLP ACROSS CNTRL IL AND SWRN IA SSWWRD ACROSS MOST OF
MO IN WHERE BREAKS IN CLOUDS HAVE ALLOWED GOOD SFC HEATING AND
RESULTING DESTABALIZATION AHEAD OF NEXT SHORT WAV CURRENTLY LIFTING
NNE FM ERN OK AND NEB. THIS SHORT WAV FCST TO MOV NE AND INTO W
CNTRL IL DURG THIS EVE...ENHANCING LO LVL CONVERCENGE ALONG AND LIFT
OVR BNDRY ACROSS NRN IL. WHILE OVERALL DURATION OF HVY RA EXPECTED
TO BE SOMEWAT LIMITED...PRECIP WATER OF 2+ INCHES SUGGESTS
TORRENTIAL DOWNPOURS PSBL SO WILL POST FLOOD WATCH GENERALLY N OF
FREEPORT TO VALPARAISO LN FOR TNGT. SHORT WAV TO CROSS THRU NERL IL
DUR EARLY FRI MORNING ENDING FLASH FLOOD POTENTIAL...THO MAIN STEM
PROBLEMS TO LINGER IF QPF POTENTIAL REALIZED. WRN PORTION OF BNDRY
LIFTS NWRD AS UPR TROF ROTATES ACROSS NRN PLAINS...WHILE BNDRY
REMAINS ACROSS NRN IL. UPR SUPPORT MISSING BUT WITH BNDRY ACROSS
AREA FRI WL CONT CHC TSTA.

.LOT...WATCHES/WARNINGS/ADVISORIES...
IL...FLOOD WATCH TONIGHT N OF FEP-VPZ LN.
IN...FLOOD WATCH TONIGHT N OF FEP-VPZ LN.
LK MI...NONE.

.AVIATION DISCUSSION FOR 18Z TAFS...

NEARLY STATIONARY FRONTAL BOUNDARY RIGHT ACROSS HEART OF FCST AREA
THIS NOON HOUR...WITH 17Z SFC ANALYSIS DEPICTING FEATURE FROM
IMMEDIATELY SOUTH OF KRFD...TO BETWEEN KDPA AND KORD...TO JUST NORTH
OF KMDW AND KGYY. IFR/LIFR TO THE NORTH OF THE FRONT WITH MVFR/VFR
TO THE SOUTH. POSITION OF FRONTAL BOUNDARY AND SUBSEQUENT LOCATION
OF IFR CONDITIONS MAIN FORECAST CHALLENGE NEXT 18-20 HOURS OR SO
WITH SIG IMPACT ON TERMINALS.

ON THE LARGER SCALE...RUC H7 ANALYSIS AND SAT LOOPS INDICATE ONE
S/WV SHEARING THROUGH IA/WRN IL INTO UPPER RIDGE...WITH SFC PRES
FALLS ALONG/NORTH OF FNT. THIS HAS ALLOWED WHAT LITTLE MOVEMENT OF
FRONT THERE IS TO BE NORTHWARD...WITH FRONT MOVING NORTH THROUGH
KMDW LAST 2 HOURS. WITH FRONT ALMOST ON TOP OF KORD BIG QUESTION IS
HOW FAR NORTH IT GOES THIS AFTN. WITH WAVE SHEARING INTO SRN WI BY
00Z...EXPECT ANY FURTHER NORTHWARD PROGRESSION TO BE
MINIMAL...THOUGH LIKELY WILL GET OVER OR THROUGH KORD. THUS HAVE
PLAYED TAFS THIS WAY...WITH WINDS COMING AROUND SW FOR AFTN HOURS
AND IMPROVEMENT IN CIG/VIS TO VFR/OCNL MVFR.

2ND S/WV LIFTING OUT OF SRN PLAINS PROGGED INTO AREA TONIGHT...WITH
GFS/ETA BOTH DEVELOPING VERTICAL MOTION MAX AROUND 06Z. HAVE TRIED
TO INDICATE MINIMUM IN RA THREAT DURING EARLY EVE HOURS BEFORE THIS
SECOND WAVE ARRIVES. BOTH GFS AND ETA DEVELOP SFC WAVE ALONG FRONT
AND PUSH IT NORTH TOWARD WISCONSIN BORDER...THOUGH SLIGHT TIMING
DIFFERENCES WITH GFS FASTER. BOTH AGREE THAT SECOND MID LEVEL TROUGH
AXIS MOVES EAST OF THE FCST AREA FRI MORN...WITH S/WV RIDGING
DEVELOPING OVER IL BY MIDDAY. THUS HAVE ENDED RA BY 14Z...THOUGH
FRONT THEN SAGS BACK SOUTH BEHIND SFC WAVE WITH NE FLOW DVLPG
KEEPING IFR CONDITIONS FOR TERMINALS.

RATZER

&&

IMPORTANT NOTICE...EFFECTIVE JUNE 15...THE AWIPS IDENTIFIER FOR
THIS PRODUCT WILL CHANGE FROM CHIAFDCHI TO CHIAFDLOT. THE WMO
HEADER

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO IL
430 PM CDT THU JUN 10 2004

ILZ003>006-008-010>014-019>022-023-032-033-039-INZ001-002-010-011-019
-111100-
WINNEBAGO-BOONE-MCHENRY-LAKE IL-OGLE-LEE-DE KALB-KANE-DU PAGE-COOK-
LA SALLE-KENDALL-GRUNDY-WILL-KANKAKEE-LIVINGSTON-IROQUOIS-FORD-
LAKE IN-PORTER-NEWTON-JASPER-BENTON-
430 PM CDT THU JUN 10 2004

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

.DAY ONE...TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING...MIANLY
SOUTH OF INTERSTATE 80. THE MAIN THREATS WITH THESE STORMS WILL
BE LARGE HAIL AND DAMAGING WINDS.

THUNDERSTORMS DEVELOPING OVER CENTRAL ILLINOIS LATE THIS AFTERNOON
MAY BECOME SEVERE AS THEY MOVE INTO AREAS SOUTH OF INTERSTATE 80
THIS EVENING.  OVERNIGHT...THESE STORMS ARE EXPECTED TO EVOLVE INTO
A THUNDERSTORM CLUSTER OVER NORTHERN ILLINOIS AND NORTHWEST
INDIANA.  THESE CONDITIONS SUPPORT AN ELEVATED RISK OF HEAVY
RAINFALL...THEREFORE...A FLOOD WATCH HAS BEEN ISSUED FOR A LARGE
PART OF NORTHERN ILLINOIS AND EXTREME NORTHWEST INDIANA.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

THUNDERSTORMS MAY BE ONGOING INTO FRIDAY MORNING.  BY FRIDAY
AFTERNOON...SHOWERS AND THUNDERSTORMS WILL BECOME ISOLATED.  THERE
WILL REMAIN A CHANCE OF THUNDERSTORMS THROUGH MONDAY...AND AGAIN
ON WEDNESDAY.  THESE STORMS ARE EXPECTED TO BE SCATTERED AND SEVERE
WEATHER IS NOT EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS EVENING.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE
NWS CHICAGO WEBPAGE: WWW.CRH.NOAA.GOV/LOT (LOWER CASE)

LMZ740>746-766-111100-
WINTHROP HARBOR IL TO NEW BUFFALO MI-
LAKE MICHIGAN-
430 PM CDT THU JUN 10 2004

THIS PORTION OF THE HAZARDOUS WEATHER OUTLOOK IS FOR THE ILLINOIS
AND INDIANA WATERS OF LAKE MICHIGAN.

.DAY ONE...TONIGHT

OCCASIONAL THUNDERSTORMS WILL DEVELOP OVER SOUTHERN LAKE MICHIGAN
THIS EVENING...AND CONTINUE OVERNIGHT.  AT THIS TIME...NONE OF
THE THUNDERSTORMS ARE EXPECTED TO BE SEVERE.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

THERE IS A CHANCE OF THUNDERSTORMS FRIDAY THROUGH MONDAY...AND AGAIN
ON WEDNESDAY.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE
NWS CHICAGO WEBPAGE: WWW.CRH.NOAA.GOV/LOT (LOWER CASE)

MERZLOCK