Severe Thunderstorm Warning 77, NWS Chicago, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
635 AM CDT MON JUL 7 2003

AVIATION DISCUSSION FOR 12Z TAFS

LINE OF TS AGAIN THIS MORNING PUSHING SE ACROSS EAST CENTRAL IA AND
FAR NW IL. CLOSE CALL AS TO HOW FAR EAST THIS LINE WILL MAKE IT THIS
MORNING BUT WILL TEMPO OUT TS FOR A FEW HRS THIS MORNING...THOUGH
MAIN PUSH OF THIS LINE IF IT HOLDS TOGETHER MAY GO SOUTH OF CHICAGO
TERMINALS. ATMOSPHERE VERY UNSTABLE AND WITH PLENTY OF OUT FLOW
BOUNDARIES CHANCE OF TS AGAIN THIS AFTERNOON AND THIS EVENING WITH
HELP FROM FRONT PUSHING SOUTH ACROSS UPPER MIDWEST. SO WILL MAINTAIN
TEMPO FOR LATE AFTERNOON THIS EVENING...BUT TS CAN/T BE RULED OUT AT
ANY TIME THRU THE PERIOD. WINDS SHOULD GO LIGHT WESTERLY TONIGHT AND
OUTSIDE OF ANY PRECIP CHANCES...MAY SEE SOME 3-5SM FOG.

CMS

DISCUSSION FOR MORNING GRIDS AND ZONES...

AS COLD FRONT SLOWLY APPROACHES FROM NW AND EVENTUALLY PUSHES THRU
CWFA PERIODS OF SHOWERS AND THUNDERSTORMS TO AFFLICT AREA NEXT
COUPLE DAYS WITH ONGOING SEVERE WEATHER THREAT AND PERHAPS BUILDING
THREAT OF FLOODING.  RECENT EVENTS CONTINUE TO SUGGEST ITS NOT
RELIABLE TO GET CUTE WITH TIMING BEYOND THE VERY SHORT TERM DUE TO
THOSE PESKY BOUNDARIES THAT DEVELOP AND FOCUS FURTHER CONVECTION AND
THE INABILITY OF ANY OPERATIONAL MODELS TO FORECAST THEM.

ONE SUCH BOUNDARY LAYING SE-NW ACROSS CWFA...PROBABLY SYNOPTIC SCALE
WARM FRONT...IS FOCUS OF MODEST BUT GENERALLY WEAKENING CONVECTIVE
DEVELOPMENT THIS MORNING.  HOWEVER RECENT ACTIVITY DEVELOPING
FURTHER W NORTH THIS WARM FRONT ON NOSE OF SOUTHWEST 850-925 FLOW
JET WOULD APPEAR LIKELY TO TRAVERSE THE AREA...ESPECIALLY
NORTH...THIS MORNING. PROBABLY ONE QUICK SHOT ALTHOUGH AS PER
SWOMCD, SOME STORMS MAY BE STRONG TO SEVERE. THEN EXPECT MORE
TSTORMS TO SPREAD EASTWARD FROM THE PLAINS/UPPER MS VALLEY TODAY AND
ARRIVE DURING THE AFTERNOON HOURS IN ASSOCIATION WITH A SHORT WAVE.
BASED ON SATELLITE/RADAR AND 06Z MODEL FORECASTS, BELIEVE THE MODELS
MAY BE A TAD SLOW WITH SHORT WAVE EMERGING FROM CENTRAL ROCKIES AND
SO WILL BEGIN PRECIP THREAT AFTER ABOUT 18Z IN FAR W.  AFTER THAT AS
MENTIONED...WILL NOT GET FANCY WITH TIMING. WILL JUST KEEP MENTION
OF TSTORMS IN THRU TUESDAY NIGHT WITH THE HIGHER POPS GRADUALLY
SHIFTING SOUTH WITH THE FRONT.  AT SOME POINT A FLOOD WATCH MAY BE
NEEDED IN THE SOUTH WHICH HAS HAD UPWARDS OF 6 INCHES RAIN LAST
COUPLE DAYS IN SOME SOUTHERN TIER COUNTIES.  DONT REALLY SEE A
HEAVY RAIN THREAT THERE TODAY HOWEVER....EXPECTED THE HEAVIER PRECIP
IN THE NORTH.

REGARDING WEDNESDAY>THURSDAY PRECIP.  GFS EXHIBITS SUSPICIOUS
BEHAVIOR SUGGESTING GRIDS SCALE FEEDBACK.  ALL OTHER MODELS SUGGEST
A WEAKER, MORE SOUTHERLY SURFACE WAVE TRACK.  FOR NOW WILL MAINTAIN
PRECIP FORECAST WED & WED NIGHT AND KNOCK IT OFF THURSDAY. WILL
TAPER POPS FROM MINIMAL IN NORTH TO BETTER CHANCE SOUTHERN SECTIONS.

WILL TEMPER HIGHS TODAY IN THE NORTH A COUPLE DEGREES FROM EARLIER
GRIDS IN LIGHT OF EXPECTED LONGER DURATION OF CLOUDS AND CONVECTIVE
THREAT.  STILL MAY PUSH 95 IN SOUTHERN COUNTIES.

.CHI...NONE

KAPLAN

ILZ003>006-008-010>014-019-020>023-032-033-039-INZ001-002-010-011-019
-081100-

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE CHICAGO IL
600 AM CDT MON JUL 7 2003

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

.DAY ONE... TODAY AND TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TODAY AND TONIGHT.
ALTHOUGH THUNDERSTORMS ARE LIKELY THIS MORNING ESPECIALLY NORTH OF I
80 MOST SHOULD REMAIN BELOW SEVERE LIMITS. THEY MAY VERY WELL
PRODUCE A LOT OF DANGEROUS CLOUD TO GROUND LIGHTNING. THE BEST
CHANCE FOR SEVERE STORMS WILL BE FROM MID AFTERNOON ON THROUGH LATE
TONIGHT. DAMAGING WINDS AND LARGE HAIL ARE THE MAIN SEVERE THREATS.

HEAT INDICES THIS AFTERNOON WILL REACH THE UPPER 90S IN MANY
AREAS...TO AROUND 105 IN SOME AREAS SOUTH OF I 80.

.DAYS TWO THROUGH SEVEN... TUESDAY THROUGH SUNDAY

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS AGAIN TUESDAY AND
TUESDAY NIGHT FOR MOST OF THE AREA.  HEAVY RAIN IS POSSIBLE
ESPECIALLY IN SOUTHERN PORTIONS...WHICH COULD CAUSE AT LEAST SMALL
STREAM FLOODING DUE TO ALREADY SATURATED SOILS FROM THE WEEKEND
RAINS...PRIMARILY SOUTHEAST OF A BLOOMINGTON...WATSEKA...RENSSELAER
LINE.

SHOWERS AND THUNDERSTORMS WILL LINGER THROUGH WEDNESDAY...BUT ARE
NOT EXPECTED TO BE SEVERE. MORE THUNDERSTORMS COULD RETURN SATURDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS MAY BE NEEDED THIS AFTERNOON...FROM MID AFTERNOON ON...AND
TONIGHT.

&&

           NWS CHICAGO WEBPAGE

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