Severe Thunderstorm Warning 179, NWS Lincoln, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
858 PM CDT TUE AUG 3 2004

.DISCUSSION...LATEST SURFACE ANALYSIS HAD A LOW CENTERED OVER
SOUTHEAST NEBRASKA...WITH ONE WARM FRONT EXTENDING NORTHEAST INTO
WISCONSIN AND ANOTHER WARM FRONT EXTENDING EAST INTO NORTHERN
ILLINOIS. A VERY WARM AND UNSTABLE AIRMASS IS IN PLACE TO THE SOUTH
OF THE SECOND WARM FRONT...WITH 00Z ILX SOUNDING SHOWING CAPE IN
EXCESS OF 5000 J/KG AND AN LI AROUND -11. WHILE THE ATMOSPHERE HAS
STABILIZED SOME WITH RESPECT TO SURFACE BASED CONVECTION...THE
INSTABILITY REMAINS ALOFT. INITIAL BOW ECHO FROM AFTERNOON
CONVECTION WILL CLIP THE NORTHERN SECTIONS OF FORECAST AREA
SHORTLY...THOUGH THE PRIMARY HIGH WIND THREAT WITH THIS BOW WILL
STAY NORTH OF OUR FORECAST AREA. A LARGE MCS IS CURRENTLY DEVELOPING
OVER WESTERN IOWA AHEAD OF THE SURFACE LOW AND ON THE NOSE OF THE
DEVELOPING LOW LEVEL JET. THIS COMPLEX SHOULD TRACK ALONG THE
OUTFLOW FROM THE INITIAL STORMS...WHICH SHOULD ALLOW IT TO TRACK
FURTHER SOUTH INTO FORECAST AREA BY LATE TONIGHT ALONG WITH AN
ASSOCIATED THREAT OF LARGE HAIL AND DAMAGING WINDS.

&&

.PREV DISCUSSION...
SHORT TERM...TONIGHT THROUGH THURSDAY...
SMALL SCALE BOW ECHO MOVING ACROSS NORTHERN IOWA EXPECTED TO STAY
PRETTY MUCH NORTH OF THE CWA THIS EVENING...HOWEVER ADDITIONAL
DEVELOPMENT STILL EXPECTED FURTHER WEST OVER EASTERN NEBRASKA AND
WESTERN IOWA AND THIS ACTIVITY WILL THREATEN AT LEAST THE NORTHERN
ZONES LATE TONIGHT. SURFACE BOUNDARY NOTED FROM CENTRAL ILLINOIS
INTO CENTRAL IOWA COULD BE THE FOCUSING MECHANISM FOR THESE STORMS.
AFTER A LULL EARLY THIS EVENING...WILL RAISE POPS INTO THE CHANCE
CATEGORY LATER THIS EVENING OVER THE WESTERN HALF OF THE AREA THEN
INTO THE LIKELY CATEGORY IN THE NORTH OVERNIGHT.

MODELS ARE BEGINNING TO CONVERGE SOMEWHAT ON A SOLUTION FOR
WEDNESDAY WITH THE SURFACE LOW ALONG THE FRONT MOVING EAST ACROSS
CENTRAL OR NORTHERN ILLINOIS BY MIDDAY WITH THE TRAILING COLD FRONT
PUSHING THROUGH THE ENTIRE AREA EXCEPT FOR THE SOUTHEAST BY 00Z.
WILL GO WITH LIKELY POPS EVERYWHERE EXCEPT FOR THE SOUTHEAST...WHERE
CONVECTION MAY BE MORE SPOTTY FURTHER SOUTH IN THE WARM SECTOR.
AMPLE MOISTURE FLOWING INTO THE SURFACE BOUNDARY TONIGHT AND EARLY
WEDNESDAY MAY LEAD TO LOCALLY HEAVY RAINFALL AMOUNTS OVER THE
NORTHERN HALF OF THE AREA AND WILL MENTION THIS IN THE ZONE
FORECASTS. PREFER THE FURTHER SOUTH SOLUTION OF THE ETA ON THE AXIS
OF HEAVIEST RAINFALL.

WILL RETAIN CHANCE POPS FOR THE EAST WEDNESDAY EVENING...THEN THE
WHOLE SYSTEM SHOULD BE PAST THE AREA BY THURSDAY MORNING. THE
FORECAST PROBLEM THEN BECOMES HOW COOL THE AFTERNOON HIGH
TEMPERATURES WILL BE. YET ANOTHER UNUSUALLY STRONG UPPER TROUGH IS
EXPECTED TO ESTABLISH ITSELF OVER THE GREAT LAKES THE LAST HALF OF
THE WEEK. 850MB TEMPERATURES ARE FORECAST TO BE AS LOW AS 7 OR 8
DEGC...BUT IT WILL BE A BATTLE BETWEEN THE COLD ADVECTION AND THE
STILL STRONG AUGUST SUNSHINE. FOR NOW WILL GO WITH MID/UPPER 70S FOR
THURSDAY AND FRIDAY...THEN A LITTLE WARMER THIS WEEKEND AS THE
AIRMASS SLOWLY MODIFIES.

LONG TERM...FRIDAY THROUGH TUESDAY...
MAINLY DRY CONDITIONS ARE EXPECTED TO PREVAIL FOR MOST OF THE LONGER
RANGE PERIOD. THE GFS WANTS TO BRING IN SOME QPF INTO THE AREA ON
MONDAY...BUT THIS MAY BE TOO SOON DEPENDING ON HOW FAST THE GREAT
LAKES UPPER TROUGH MOVES OUT. WILL PUT IN LOW CHANCE POPS FOR
TUESDAY BUT MAY NEED TO ADJUST THE TIMING AS THAT TIME FRAME GETS
CLOSER.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
IL...NONE.

&&

BAK/04

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LINCOLN IL
324 PM CDT TUE AUG 3 2004

ILZ027>031-036>038-040>057-061-041100-
CASS-CHAMPAIGN-CHRISTIAN-COLES-DE WITT-DOUGLAS-EDGAR-FULTON-KNOX-
LOGAN-MACON-MARSHALL-MASON-MCLEAN-MENARD-MORGAN-MOULTRIE-PEORIA-
PIATT-SANGAMON-SCHUYLER-SCOTT-SHELBY-STARK-TAZEWELL-VERMILION-
WOODFORD-
INCLUDING THE CITIES OF...BLOOMINGTON...CHAMPAIGN...DANVILLE...
DECATUR...GALESBURG...HAVANA...JACKSONVILLE...LINCOLN...MATTOON...
PEORIA...SHELBYVILLE...SPRINGFIELD AND TAYLORVILLE
324 PM CDT TUE AUG 3 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL ILLINOIS.

.DAY ONE...TODAY AND TONIGHT

THERE IS A RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON AND
TONIGHT...MAINLY ALONG AND WEST OF INTERSTATE 70. THE PRIMARY THREAT
WILL BE FROM DAMAGING WINDS AND LARGE HAIL. HEAVY RAINS WILL ALSO BE
POSSIBLE LATER TONIGHT...MAINLY ALONG AND WEST OF THE ILLINOIS RIVER.
DEPENDING ON THE TRACK OF THE SYSTEM...DAMAGING WINDS COULD BE A
SIGNIFICANT THREAT TONIGHT ACROSS PARTS OF CENTRAL ILLINOIS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY
A LOW PRESSURE SYSTEM WILL MOVE A COLD FRONT THROUGH THE AREA ON
WEDNESDAY. THERE WILL BE A SLIGHT CHANCE FOR SEVERE STORMS WEDNESDAY
AND WEDNESDAY NIGHT. DAMAGING WINDS...LARGE HAIL AND HEAVY RAINS WILL
BE POSSIBLE.

.SPOTTER ACTIVATION STATEMENT...

SPOTTER ACTIVATION WILL LIKELY BE REQUIRED THIS EVENING AND TONIGHT.

ILZ062-063-066>068-071>073-041100-
CLARK-CLAY-CRAWFORD-CUMBERLAND-EFFINGHAM-JASPER-LAWRENCE-RICHLAND-
INCLUDING THE CITIES OF...EFFINGHAM...FLORA AND LAWRENCEVILLE
324 PM CDT TUE AUG 3 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST ILLINOIS.

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT CHANCE FOR SEVERE THUNDERSTORMS TONIGHT
ACROSS PARTS OF SOUTHEAST ILLINOIS. THE PRIMARY THREAT AREA WILL BE
MAINLY ALONG AND NORTHWEST OF INTERSTATE 70. DAMAGING WINDS AND LARGE
HAIL WILL BE THE PRIMARY THREAT FROM THESE STORMS.

.DAYS TWO THROUGH SEVEN... WEDNESDAY THROUGH MONDAY

A LOW PRESSURE SYSTEM WILL MOVE A COLD FRONT THROUGH THE AREA ON
WEDNESDAY. THERE WILL BE A SLIGHT CHANCE FOR SEVERE STORMS WEDNESDAY
AND WEDNESDAY NIGHT. DAMAGING WINDS...LARGE HAIL AND HEAVY RAINS WILL
BE POSSIBLE WITH THIS SYSTEM.

.SPOTTER ACTIVATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED TONIGHT AND ON WEDNESDAY ACROSS
PARTS OF SOUTHEAST ILLINOIS.

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