Severe Thunderstorm Warning 3, NWS Chicago, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
1235 PM CDT WED APR 30 2003

AVIATION DISCUSSION FOR 18Z TAFS...
WMFNT FM KS LOW NEWRD ALONG MO/IA BORDER ACROSS NRN IL...S OF
TERMINALS...INTO NRN IND LIFTING NWRD. FIRST WAVE OF TS FM SCNTRL WI
ACROSS NW IL INTO SW IA TO MOV ACROSS TERMINALS DURG AFTERNOON...AND
SHUD SLO NWRD PROGRESS OF FNT IN FAR NRN IL WHERE WILL STALL. INCRG
DWPTS WITH ERLY COMPONENT OFF COLD LAKE RESULTING IN AREAS OF IFR
CIGS AND EXPECTED TO PERSIST TIL LATER AFTERNOON WHEN SFC FLO
BECOMES SERLY. CONVECTION SHUD BE ENUF TO MIX THIS LOWER LAYER OUT
TEMPO. NEXT ROUND TO ARIVE MID-LATE EVE AS SHORT WAV CROSSES MS
RIVER. WK ASSOCIATED SFC WAV INDICATED IN SFD WND FIELD TO MOVE OVER
SRN LK MI BY 06Z...WITH BNDRY SHIFTING BACK S OF ORD & MDW TERMINAL
AREAS. ANOTHER WAV/VORT MAX MOVS NE TO MS RIVER BY 12Z TO SPAWN
ANOTHER WAVE OF TS FOR REGION 12-18Z THU.

PUBLIC DISCUSSION FOR 4AM ZONES/GRIDS

FORECAST CONCERNS CONTINUE TO FOCUS ON CHANCE OF THUNDERSTORMS AND
THREAT OF SVR THRU THURS EVENING. LARGE AREA OF TS EXTENDS FROM
WESTERN IL BACK INTO NE AT 06Z AND EXPANDING ENE ALONG AND AHEAD OF
WARM FRONT. MODELS IN BETTER AGREEMENT THIS PACKAGE LIFTING WARM
FRONT ACROSS NORTHERN THIRD OF CWA BY LATE THIS PM. EXPECTING
OCCASIONAL TSRA TO CONTINUE MOST OF THE DAY NORTH THIRD CWA...WITH
LIKELY CENTRAL AND CHANCE SOUTH. WIDE RANGE IN TEMPS TODAY AS
ANYWHERE SOUTH OF THE FRONT SHOULD EASILY MAKE MID 70S AND WITH
ENOUGH SUN EVEN WARMER...PROBABLY LOW 80S SOUTHERN CWA ALONG WITH
SFC DEWPOINTS INTO THE LOWER 60S. SVR WX A CONCERN WITH MESOETA
SHOWING CAPES 1000-1500J/KG AND LI/S TO -4 ACROSS MUCH OF CWA SOUTH
OF WARM FRONT. MDT RISK INTO OUR WESTERN CWA PER LATEST SWODY1 AND
THINK WITH ALL THE INSTABILITY AROUND TODAY THAT THREAT MAY NEED TO
BE EXTENDED EAST INTO FAR NW IN AND HAVE COLLABORATED WITH SPC TO
HAVE MENTION OF MDT RISK IN AM HWO.

COLD FRONT THEN PROGGED INTO NORTHERN CWA 09Z-12Z THURS MORNING
MAKING SLOW PROGRESS SOUTH DURING THE DAY THURS. TSRA LIKELY TONIGHT
THEN CHANCE THURS WITH BEST CHANCES ALONG EASTERN 1/3 OF CWA INTO
THURS PM. THREAT OF SVR POSSIBLE THURS MAINLY ACROSS SOUTHEAST CWA.
TEMPS TONIGHT JUST AS HARD AS TODAY BUT CONSENSUS THE BEST BET WITH
LOWER 50S NORTH TO MID 60S SOUTH. COOLER ALONG THE LAKE THURS WITH
NORTHERLY FLOW. CONSENSUS ON TEMPS FOLLOWED INTO FRI AS WELL.

.CHI...NONE.

CMS

ILZ003>006-008-010>014-019-020>023-032-033-039-INZ001-002-010-011-019
-011100-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO IL
1210 PM CDT WED APR 30 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 MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN
ILLINOIS THIS AFTERNOON AND TONIGHT. THERE IS A SLIGHT RISK OF
SEVERE
THUNDERSTORMS ACROSS NORTHWEST INDIANA.

SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH EARLY
AFTERNOON...MAINLY NORTH OF INTERSTATE 80.   AFTER 3 PM THERE WILL
BE INCREASING CHANCES OF STRONG TO SEVERE THUNDERSTORMS DEVELOPING
OVER NORTHERN ILLINOIS AND AFTER 5 PM INTO NORTHWEST INDIANA.

A WARM FRONT WILL LIFT INTO NORTHERN ILLINOIS AND INDIANA AND THEN
BECOME STATIONARY JUST SOUTH OF LAKE MICHIGAN THIS EVENING. THE
ATMOSPHERE IS EXPECTED TO BECOME VERY UNSTABLE NEAR AND SOUTH OF THE
WARM FRONT. THE MAIN SEVERE WEATHER THREAT WILL BE LARGE HAIL AND
DAMAGING WINDS. ISOLATED TORNADOES WILL BE POSSIBLE NEAR THE WARM
FRONT.

.DAYS TWO THROUGH SEVEN... THURSDAY THROUGH TUESDAY

A COLD FRONT WILL PUSH SOUTHEAST ACROSS NORTHERN ILLINOIS AND
NORTHWEST INDIANA THURSDAY MORNING. THUNDERSTORMS WILL BE POSSIBLE
THURSDAY MORNING AND AFTERNOON. THERE IS A SLIGHT CHANCE THAT SOME
OF THESE THUNDERSTORMS MAY BE SEVERE SOUTH OF A PONTIAC TO KANKAKEE
ILLINOIS TO VALPARAISO INDIANA LINE. THE THREAT OF THUNDERSTORMS
WILL END BY LATE AFTERNOON.

A SMALL CRAFT ADVISORY MAY BE NEED THURSDAY NIGHT FOR THE NEARSHORE
WATERS OF LAKE MICHIGAN ALONG THE ILLINOIS AND INDIANA SHORES FOR
STRONG WINDS AND HIGH WAVES.

THERE IS ANOTHER CHANCE FOR THUNDERSTORMS ON MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS WILL LIKELY BE NEEDED LATE THIS AFTERNOON AND TONIGHT.

&&

           NWS CHICAGO WEBPAGE

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

AF