Tornado Warning 57, NWS Chicago, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
316 PM CDT TUE AUG 24 2004

.DISCUSSION...

MAIN FOCUS ON SHORT TERM AND THUNDERSTORMS. RADAR CURRENTLY SHOWING
BAND OF THUNDERSTORMS MOVG NE ACROSS EASTERN PORTIONS OF FCST
AREA...ASSOCIATED WITH INSTABILITY AXIS AND RELATIVELY STRONG MID
LEVEL WAVE MOVING SLOWLY NORTHEAST ACROSS AREA. WATER VAPOR AND
PROFILER DATA INDICATES MID LVL TROF AXIS MOVG THRU CWA NEXT SVRL
HOURS...WITH VIS SATELLITE SHOWING SIGNS OF SUBSIDENCE ACROSS W
CNTRL IL BEHNIND WAVE AND MCS ACROSS MO/SW IL. WILL KEEP CATEGORICAL
POPS THRU REMAINDER OF AFTN AHEAD OF WHERE CONVECTION CURRENTLY
LOCATED...MAINLY CHI AND NW IND OUT OVER LAKE MI...THEN SCALE BACK
TO CHANCE BY EVENING AS SYNOPTIC FORCING MOVES NORTH THOUGH WEAK
LLVL MOISTURE ADVECTION CONTINUES. NEXT WAVE EVIDENT OVER WRN NEB/KS
TO APPROACH THE AREA LATER TONIGHT AND WED. MODELS INDICATE H85
THETA-E RIDGE AND MOIST CONVERGENCE MAX VCNTY NRN MO...AND EXPECT
MCS DVLPMENT OVERNGT SW OF FCST AREA. EXPECT INCREASE IN RW/TRW
COVERAGE AGAIN BY LATE WED MORN...THOUGH WITH AFFOREMENTIONED
CONTINUES WAA/MOIST ADVECTION WILL NOT GET CUTE WITH TRYING TO TIME
CONVECTIVE BANDS.

AS THIS SECOND WAVE EJECTS NORTHEASTWARD BY THURSDAY...GFS AND ETA
BOTH SHOWING UPSTREAM FLOW BECOMING LESS AMPLIFIED WITH LESS OF A
SPLIT FLOW. THIS KEEPS NEXT WAVE NORTH OF FA...SUGGESTING RELATIVELY
DRY PERIOD THURS/THURS NGT. NEW 12Z RUNS ARE NOW FASTER WITH
APPROACHING FRONT FOR END OF WEEK...AND NOW BRING IT INTO THE FCST
AREA FRI MORNING RATHER THAN LATE SATURDAY. HAVE TRIED TO BLEND
TOWARD A SLIGHTLY FASTER SOLUTION WITHOUT MAKING MASSIVE CHANGES TO
THE EXTENDED...AND TO KEEP IN BALANCE WITH SURROUNDING WFO GRIDS.
FCST TRENDED IN RIGHT DIRECTION IF SUCCESSIVE RUNS CONTINUE FASTER
FROPA.

RATZER

&&

.AVIATION...

NARROW LINE OF TS MOVING NORTH/NORTHEAST ACROSS CENTRAL IL LATE
THIS MORNING/EARLY THIS AFTERNOON. EXPECT THIS LINE TO MAINTAIN
ITSELF AND PUSH THRU DPA 18Z-20Z THEN ORD/MDW 19Z-21Z. DIFFICULT TO
TIME ANY OTHER TS...OR PRECIP FOR THAT MATTER...REST OF THE PERIOD.
HAVE OPTED TO CARRY CHANCE OF SHOWERS LATE THIS AFTERNOON AND EARLY
THIS EVENING THEN APPEARS THERE WILL BE A DRY PERIOD INTO THE
OVERNIGHT HRS. ANOTHER CHANCE OF SHOWERS/TS TOWARD THE END OF THE
PERIOD BUT WILL LEAVE OUT MENTION THIS CYCLE AND LET LATER RUNS PIN
DOWN BETTER TIMING. CIGS AND VIS ALSO PROBLEMATIC. EXPECT VFR CIGS
TO SLOWLY LOWER THRU MVFR DURING THE LATE AFTERNOON AND EVENING.
HAVE TAKEN ORD/MDW/GYY TO LOW MVFR OVERNIGHT WITH CIGS AROUND 1KFT
WITH IFR CIGS CERTAINLY POSSIBLE. WINDS STAY MAINLY SSE THRU THE
PERIOD WITH SPEEDS DIMINISHING TO 5KTS OR SO OVERNIGHT.

&&

.LOT...WATCHES/WARNINGS/ADVISORIES...
.IL...NONE.
.IN...NONE.
.LK MI...NONE.

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CHICAGO IL
430 PM CDT TUE AUG 24 2004

ILZ003>006-008-010>014-019>022-023-032-033-039-INZ001-002-010-011-019
-251100-
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 TUE AUG 24 2004

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

.DAY ONE... TONIGHT

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. ISOLATED TO
SCATTERED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE OVERNIGHT AS AN
UPPER LEVEL DISTURBANCE MOVES ACROSS THE AREA.

.DAYS TWO THROUGH SEVEN... WEDNESDAY THROUGH MONDAY

ON WEDNESDAY AFTERNOON THERE IS A SLIGHT RISK OF SEVERE
THUNDERSTORMS WEST OF INTERSTATE 39. THERE IS ALSO A SLIGHT RISK OF
SEVERE THUNDERSTORMS ON THURSDAY FOR NORTHWEST ILLINOIS.
THUNDERSTORMS WILL ALSO BE POSSIBLE ACROSS THE AREA FRIDAY NIGHT
THROUGH SATURDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME.

&&

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

LMZ740>746-766-251100-
WINTHROP HARBOR IL TO NEW BUFFALO MI-
LAKE MICHIGAN-
430 PM CDT TUE AUG 24 2004

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

.DAY ONE... TONIGHT

THUNDERSTORMS OVER SOUTHERN LAKE MICHIGAN LATE THIS AFTERNOON WILL
DISSIPATE THIS EVENING...THOUGH THERE WILL REMAIN A SLIGHT CHANCE OF
ADDITIONAL ISOLATED SHOWERS AND THUNDERSTORMS OVERNIGHT AS AN UPPER
LEVEL DISTURBANCE MOVES ACROSS THE AREA. BRIEF HEAVY RAIN AND WIND
GUSTS TO 30 KNOTS ARE POSSIBLE INTO EARLY EVENING.

.DAYS TWO THROUGH SEVEN... WEDNESDAY THROUGH MONDAY

ON WEDNESDAY INTO THURSDAY...THUNDERSTORMS WILL BE POSSIBLE.
THUNDERSTORMS ARE ALSO POSSIBLE FRIDAY NIGHT THROUGH SATURDAY NIGHT.

&&

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