Severe Thunderstorm Warning 33, NWS Chicago, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
210 PM CDT WED MAY 14 2003

PUBLIC DISCUSSION FOR 330PM ZONES/GRIDS

MORNING PRECIP KEEPING FAR NORTHERN FA CLOUDY/COOL AS FRONT LIES
ACROSS SOUTHWEST FA FROM ROUGHLY LA SALLE TO IROQUOIS COUNTY. BEST
INSTABILITY AND SUNSHINE SOUTH OF THIS FRONT AS STORMS HAVE FIRED
ACROSS QUAD CITIES LAST 1-2 HRS. THIS AREA OF TSRA TO MOVE ESE THRU
THE AFTERNOON/EARLY EVENING WITH MAIN SVR THREAT BEING LARGE HAIL
ACROSS SOUTHWEST COUNTIES. PRECIP DIMINISHES DURING THE EVENING
HOURS AS FIRST VORT EXITS BUT CONVECTION CURRENTLY FIRING ACROSS MN
NORTH CENTRAL IA...ASSOCIATED WITH SECOND VORT ROTATING AROUND UPPER
LOW TO BRING ANOTHER CHANCE OF -TSRA OVERNIGHT. UPPER LOW MAKES IT
AS FAR SOUTH AS SOUTHERN GREAT LAKES BEFORE STALLING THEN WEAKENING
INTO FRIDAY SO SHOWERS AGAIN POSSIBLE DURING THE DAY THURS. AS UPPER
LOW WEAKENS...HIGH PRESSURE BUILDS ACROSS EASTERN LAKES INTO THE
WEEKEND. NEXT SYSTEM DEVELOPS OVER THE PLAINS FRIDAY NIGHT AND TRIES
TO LIFT NORTHEAST SAT/SAT NIGHT. UNCERTAINTY AS TO HOW FAR NORTH...
HOW STRONG EASTERN LAKES HIGH WILL BE SO WILL CONTINUE WITH DRY
FORECAST FOR NOW BUT TREND IS TO BRING SYSTEM FURTHER NORTH. WARMUP
INTO EARLY NEXT WEEK THEN NEXT SYSTEM COMES THRU TUES NIGHT/WED AND
HAVE INCLUDED PRECIP. HAVE TRENDED TOWARD A BLEND OF GUIDANCE FOR
TEMPS IN THE SHORT TERM WITH COOLER ALONG THE LAKE WITH NE FLOW.

.CHI...NONE.

CMS

AVIATION DISCUSSION FOR 18 UTC TAFS

MAIN CONCERN NXT 6 HRS WILL BE TSTMS.  COLD POOL ALF MOVG SEWD INTO
IA...SWRN WI...NRN/CNTRL IL WILL INCRS TSTM THREAT THRU AFTN/ERLY
EVENING HRS.  VIS SATLT IMAGERY THRU NOON CDT HAS SHOWN CLOUDINESS
OVR ERN IA/NWRN IL BCMG INCREASINGLY CONVECTIVE AND RADAR PAST HR
HAS SHOWN MARKED INCRS IN TSTM COVG AND ITENSITY.  ATMOSPHERIC
TEMP/MOISTURE PROFILES SUGGEST HIGH PROBABILITY OF HAIL IN STGR
CELLS.  CIGS WILL BE GENLY MVFR...BUT WILL BE QUITE VRBL DUE TO
CONVECTIVE NATURE OF WX...VARYING BTWN BKN CIGS NR FL012 TO VFR OVC
ARND FL060.  VIS GENLY OK...AOA 5SM BUT LCLLY BLO 3SM IN
SHWRS/TSTMS.  SHWRS/TSTMS EXPECTED TO DMNSH AFT SS AS LOWER
ATMOSPHERE STABILIZES.  WINDS ELY-ESELY THIS AFTN SHUD MAINTAIN
STABILIZING INFLUENCE IN CHI AREA DUE TO COOL AIR OFF LK MI.
HOWEVER...THIS FLOW WILL CONTINUE THRU TAF PERIOD AND WILL BE
CONDUCIVE TO MORE SOLID MVFR CIGS BY THIS EVENING.

MERZLOCK

ILZ003>006-008-010>014-019-020>023-032-033-039-INZ001-002-010-011-019
-151100-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO IL
420 PM CDT WED MAY 14 2003

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

.DAY ONE... TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS MAINLY IN THE
EARLY EVENING...GENERALLY SOUTH AND WEST OF A LINE FROM
ROCKFORD...TO KANKAKEE...TO RENSSELAER INDIANA.

LOW PRESSURE WILL MOVE SOUTHEAST ACROSS IOWA THIS AFTERNOON...AS A
STATIONARY FRONT EXTENDS EASTWARD ACROSS CENTRAL ILLINOIS AND
INDIANA. COOLING TEMPERATURES ALOFT WILL HELP DESTABILIZE THE
ATMOSPHERE...ESPECIALLY IN THE VICINITY OF THE FRONT. THE SEVERE
THREAT WILL DIMINISH AFTER SUNSET AS LOW LEVEL TEMPERATURES COOL.
DUE TO THE PARTICULARLY COLD TEMPERATURES ALOFT...THE PRIMARY SEVERE
THREAT WILL BE LARGE HAIL. WIND PROFILES APPEAR RATHER WEAK SO
DAMAGING WINDS ARE LESS LIKELY. THIS TYPE OF ATMOSPHERE MAY ALSO
PROMOTE THE DEVELOPMENT OF COLD AIR FUNNELS IN ASSOCIATION WITH
RAPIDLY BUILDING CUMULONIMBI. FARTHER TO THE NORTH OF THE WARM
FRONT...LESS INSTABILITY ACROSS NORTHEAST ILLINOIS AND EXTREME
NORTHWEST INDIANA WILL TEND TO LIMIT THE SEVERE THREAT...ESPECIALLY
ACROSS NORTHEAST ILLINOIS WHERE COOL EASTERLY WINDS OFF LAKE
MICHIGAN WILL KEEP THE LOWER ATMOSPHERE RELATIVELY STABLE. ALTHOUGH
ELEVATED THUNDERSTORMS MAY OCCUR IN THESE AREAS...THEY ARE NOT
EXPECTED TO BE SEVERE.

.DAYS TWO THROUGH SEVEN... THURSDAY THROUGH TUESDAY

THE NEXT CHANCE OF THUNDERSTORMS WILL BE TUESDAY NIGHT OR WEDNESDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS WILL NOT BE NEEDED.

&&

           NWS CHICAGO WEBPAGE

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