Severe Thunderstorm Warning 53, NWS Chicago, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
225 AM CDT SAT JUL 5 2003

PUBLIC DISCUSSION FOR MORNING GRIDS/ZONES...

SYNOPSIS...SERIES OF UPPER AIR DISTURBANCES WILL CONTINUE TO SPAWN
CLUSTERS OF THUNDERSTORMS ACROSS THE UPPER MISSISSPPI VALLEY AND
GREAT LAKES INTO MIDWEEK. MOST OF THESE EVENTS WILL BE NOCTURNAL OR
EARLY MORNING.

DISCUSSION...PERSISTENT DEPRESSED WESTERLY STREAM WITH EMBEDDED
IMPULSES WILL KICK OFF TSTM CLUSTERS ACROSS THE NORTHERN PLAINS
DURING THE NEXT SEVERAL DAYS WITH THESE MOVING THROUGH THE SOUTHERN
LAKES THEREAFTER.  ONE CLUSTER NOW BOWING OUT THROUGH EASTERN IOWA
WILL RUSH ACROSS NORTHERN ILLINOIS DURING THE ENXT FEW HOURS. THIS
ONE SUPPORTED BY RR QUAD OF RETREATING 125KT UPPER JET PROGGED TO
MOVE ACROSS UP OF MICH AND NORTHERN THUMB THIS MORNING.  700-500MB
FLOW OF 25-45KTS EXPECTED DURING THESE NEXT SEVERAL EVENTS SO BOWING
THREAT LIKELY TO BE THE MAIN THREAT FOR THE NEXT FEW DAYS.

MODELS...WHILE ALWAYS DOUBTED IN THESE CONVECTIVE SITUATIONS... ARE
VALID IN THE OVERALL PATTERN AND MAY BE RIGHT IN HAVING THESE
NOCTURNAL EVENTS FOR NRN ILLINOIS. SORT OF A 24HR CYCLE. APPEARS
THAT SAT NIGHT AND AGAIN SUN NIGHT MAY BE PLAGUED BY A TSTM THREAT
IN THIS AREA.  BY MON-TUE A MORE DEFINED AMPLIFICATION IS FORECAST
WHICH SHOULD INITIATE A BETTER DEFINED SURFACE CYCLONE MOVING ACROSS
THE LAKES EARLY WEDNESDAY.  THIS SUGGESTS MON AND PERHAPS TUE WILL
BE WARMER DAYS IN MORE SUSTAINED SW FLOW WHILE FINAL ROUND OF
CONVECTION TUE NIGHT COULD BE SYNOPTICALLY ORGANIZED.

TEMPS NOT VARYING MUCH NEXT SEVERAL DAYS WITH MAXS A FUNCTION OF
SUNSHINE AND CLEARING BEHIND THESE CLUSTERS. CONTINUING MUGGY.  WILL
AVERAGE UPPER 80S OR LOW 90S MOST SPOTS NEXT 2 DAYS THEN LOW 90S OR
SO MON-TUE BEFORE HEADING INTO THE UPPER 70S WED. POPS GENERALLY
BROAD BRUSHED DUE TO UNCERTAINTIES IN TIMING BUT HIGHER AT NIGHT. KL

.CHI...NONE

.CHI...NONE

MERZLOCK

ILZ003>006-008-010>014-019-020>023-032-033-039-INZ001-002-010-011-019
-051100-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO IL
200 AM CDT SAT JUL 5 2003

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

.DAY ONE...PREDAWN HOURS

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER MUCH OF
NORTHERN ILLINOIS AND NORTHWEST INDIANA. SEVERE THUNDERSTORM WATCH
NUMBER 641 IS IN EFFECT FOR LEE...OGLE AND WINNEBAGO COUNTIES UNTIL
600 AM.

ANOTHER ACTIVE CLUSTER OF THUNDERSTORMS IS MOVING ACROSS EASTERN
IOWA AND WILL REACH THE MISSISSIPPI RIVER BEFORE 3AM.  OTHER
THUNDERSTORMS ARE FORMING ALONG A LINE FROM NEWTON AND JASPER
COUNTIES INDIANA NORTHWEST INTO LEE COUNTY ILLINOIS.

THE STORMS MOVING ACROSS IOWA INTO NORTHWEST ILLINOIS IN THE NEXT
FEW HOURS POSE A WIND DAMAGE THREAT. THEY ARE EXPECTED TO MOVE
ACROSS THE REMAINDER OF NORTHERN ILLINOIS BY OR BEFORE SUNRISE.

THE STORMS FORMING FROM INDIANA INTO NORTHWEST ILLINOIS MAY POSE A
LOCAL FLOOD THREAT DURING THE PREDAWN HOURS. THEY WILL MERGE WITH
THE IOWA STORMS AS TIME GOES ON.

.DAYS TWO THROUGH SEVEN... SATURDAY THROUGH THURSDAY

THERE IS A CHANCE OF THUNDERSTORMS AGAIN SATURDAY NIGHT INTO SUNDAY
MORNING...AND AGAIN SUNDAY NIGHT THROUGH TUESDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED IN THE NEXT FEW HOURS.

&&

           NWS CHICAGO WEBPAGE

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

KL