Damaging Wind in Illinois, August 18, 2005

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
530 AM CDT THU AUG 18 2005

.DISCUSSION...
HOT...HUMID AND ACTIVE WEATHER PATTERN EXPECTED FOR CENTRAL IL
THROUGH SAT WITH WARM FRONT MOVING NE THROUGH CENTRAL IL TODAY
AND A STRONG COLD FRONT SLIDING SE THROUGH THE STATE SAT. FORECAST
CHALLENGE IS ADDRESSING CONVECTION CHANCES AND SEVERE WEATHER RISK
AND HOW HOT IT GETS THROUGH SAT. THEN LOOKING AT HOW MUCH COOLER IT
GETS BEHIND THE COLD FRONT EARLY NEXT WEEK. GFS WAS PREFERRED MODEL
BY NCEP THOUGH SUFFERING FROM CONVECTIVE FEEDBACK. GUIDANCE TEMPS
SIMILAR AND FOLLOWED THROUGH SAT...EXCEPT WENT A FEW DEGREES COOLER
FOR HIGHS TODAY.

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT
DAWN SURFACE ANALYSIS HAS 1003 MB LOW PRESSURE OVER SE SD WITH A
WARM FRONT EXTENDING ACROSS CENTRAL IOWA INTO SW IL FROM JUST NORTH
OF A QUINCY TO EVANSVILLE LINE. 1022 MB HIGH PRESSURE WAS OVER
WESTERN QUEBEC AND RIDGING SOUTH ACROSS THE ATLANTIC STATES. MUGGY
TEMPS WERE NEAR DEWPOINTS IN THE UPPER 60S AND LOWER 70S WITH LIGHT
SE WINDS. A BIT OF FOG FROM THE IL RIVER SE WITH VSBYS 1 TO 2 MILES.
MOST OF CENTRAL IL HAS BEEN DRY SO FAR THIS MORNING. WIDELY
SCATTERED LINE OF CONVECTION LIFTED NE INTO NE IL AND NW INDIANA
WITH ELEVATED WARM FRONT. AN AREA OF SCATTERED CONVECTION WAS FROM
ROBINSON AND LAWRENCEVILLE SOUTH INTO WESTERN KY AND DRIFTING EAST.
ANOTHER AREA OF MORE SOLID CONVECTION WITH AN MCS OVER CENTRAL MO
MOVING EAST TOWARD ST LOUIS. AND A THIRD AREA OF CONVECTION WITH AN
MCS WAS OVER EASTERN IOWA AND SW WI MOVING ENE.

WARM FRONT IS PROGGED TO LIFT NE ACROSS CENTRAL IL TODAY WITH AN
INCREASING CHANCE OF CONVECTION FROM WEST TO EAST AS THE DAY
PROGRESSES AS ATMOSPHERE BECOMES MORE UNSTABLE THIS AFTERNOON WITH
LIFTED INDICES OF MINUS 5-7C AND MLCAPES 2000 TO 3000 J/KG. UPPER
LEVEL SHORT WAVE OVER WESTERN MN/IA TO MOVE EAST ACROSS NORTHERN IL
AND WI THIS AFTERNOON WHILE 40 TO 50 KNOT 500 MB JET MOVES EAST
TOWARD CENTRAL IL BY SUNSET. SO INCREASING WIND SHEAR ALONG WITH
HIGH INSTABITLY SUPPORTS AT LEAST SLIGHT RISK OF SEVERE STORMS
PER SPC LATER THIS AFTERNOON AND EVENING ESPECIALLY FROM 3 TO 9 PM.
GREATEST SEVERE THREAT IS LARGE HAIL AND DAMAGING WIND GUSTS
ESPECIALLY NORTH OF I-70. SUPERCELLS WITH ISOLATED TORNADOES WILL BE
MORE LIKELY OVER NORTHERN IL...EASTERN IOWA AND SOUTHERN WI. HEAVY
RAIN POSSIBLE TOO WITH PRECIPITABLE WATER VALUES 1.5 TO 2 INCHES.
HIGHS HAVE BEEN 1 TO 3 DEGREES COOLER THAN MAV PAST TWO DAYS AND
WILL FOLLOW THAT ROUTE TODAY WITH UPPER 80S MOST AREAS AND HUMID AS
DEWPOINTS ELEVATE INTO THE LOW TO MID 70S. CONVECTION CHANCES SHOULD
DIMINISH OVERNIGHT ESPECIALLY SOUTHERN AREAS AS WARM FRONT LIFTS
NORTH OF CENTRAL IL.

UPPER LEVEL RIDGING INTO CENTRAL IL FRI LOOKS TO KEEP MOST AREAS DRY
ALONG WITH AND HOT AND HUMID CONDITIONS. KEPT SLIGHT CHANCE OF
CONVECTION AND BEST FORCING TO BE NORTH AND WEST OF AREA FRI. HOT
FRI WITH HIGHS NEAR 95F AND DEWPOINTS IN THE 70S GIVES AFTERNOON
HEAT INDEX READINGS 100 TO 105 WITH SE IL AROUND 105F WHERE MORE
SUNSHINE POSSIBLE AND HEAT ADVISORY MAY BE NEEDED HERE. CONVECTION
CHANCES INCREASE AGAIN ESPECIALLY NW OF I-70 FRI NIGHT STRONG CUTOFF
UPPER LEVEL LOW OVER SOUTHERN ALBERTA MOVES TO JUST NORTH OF MN BY
DAWN SAT AND DRIVES A STRONG COLD FRONT SE INTO NW IL. SPC HAS
SLIGHT RISK OF SEVERE THUDNERSTORMS FRI NIGHT NW OF THE IL RIVER
WITH MCS MOVING OUT OF IOWA. THIS FRONT TO SLIDE SE THROUGH CENTRAL
IL SAT AND BE NEAR THE OHIO RIVER BY SUNSET SAT. SPC HAS SLIGHT RISK
OF SEVERE STORMS NE OF AREA SAT BUT WILL NEED TO BE WATCHED.
CONVECTION CHANCES LOOK TO DIMINISHED FROM NW TO SE SAT AFTENOON
INTO EARLY SAT EVENING. MOST OF AREA LOOKS DRY BY SAT NIGHT...THOUGH
DID KEEP A SMALL CHANCE OF CONVECTION OVER SE IL THEN. GFS IS SLOWER
WITH COLD FRONT THAN NAM.

.LONG TERM...SUNDAY THROUGH THURSDAY
DRY...COOLER AND LESS HUMID WEATHER PREVAILS EARLY NEXT WEEK BEHIND
THE COLD FRONT AS CANADIAN HIGH PRESSURE BUILDS INTO THE MIDWEST AND
STICKS AROUND THROUGH MID WEEK ENSURING DRY WEATHER. COOLED TEMPS A
FEW DEGREES EARLY NEXT WEEK TO BELOW NORMAL LEVELS PER COOLER 850 MB
TEMPS. TEMPS MODERATE BACK TO NORMAL BY THE SECOND HALF OF THE WEEK
WITH HIGH PRESSURE SLIPPING OFF THE EAST AND UPPER LEVEL RIDGING
INTO IL AND THE OHIO VALLEY.

&&

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

HUETTL

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE LINCOLN IL
730 AM CDT THU AUG 18 2005

CORRECTED SPOTTER ACTIVATION SECTION

ILZ027>031-036>038-040>057-061>063-066>068-071>073-191100-
KNOX-STARK-PEORIA-MARSHALL-WOODFORD-FULTON-TAZEWELL-MCLEAN-
SCHUYLER-MASON-LOGAN-DE WITT-PIATT-CHAMPAIGN-VERMILION-CASS-
MENARD-SCOTT-MORGAN-SANGAMON-CHRISTIAN-MACON-MOULTRIE-DOUGLAS-
COLES-EDGAR-SHELBY-CUMBERLAND-CLARK-EFFINGHAM-JASPER-CRAWFORD-
CLAY-RICHLAND-LAWRENCE-
730 AM CDT THU AUG 18 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST
ILLINOIS...CENTRAL ILLINOIS AND EAST CENTRAL ILLINOIS.

.DAY ONE...TODAY AND TONIGHT

A WARM FRONT WILL LIFT NORTHWARD THROUGH THE AREA TODAY AND
COMBINE WITH INCREASING LOW LEVEL MOISTURE TO PRODUCE
THUNDERSTORMS ACROSS THE AREA...MAINLY LATE THIS AFTERNOON AND
INTO TONIGHT. THERE IS A SLIGHT RISK THAT SOME OF THESE STORMS
COULD BECOME SEVERE...WITH DAMAGING WINDS AND HAIL THE MAIN
THREAT. ISOLATED TORNADOES ARE ALSO POSSIBLE NORTH OF INTERSTATE
72.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

A FRONTAL SYSTEM WILL REMAIN OVER THE AREA FRIDAY AND BRING
ANOTHER ROUND OF THUNDERSTORMS TO THE AREA FRIDAY NIGHT AND
SATURDAY. THERE IS A SLIGHT RISK OF SEVERE WEATHER NORTHWEST OF
THE ILLINOIS RIVER FOR FRIDAY NIGHT.

IN ADDITION...HOT AND HUMID WEATHER WILL RETURN TO THE AREA FRIDAY
AFTERNOON WITH HEAT INDEX VALUES OF 100 TO 105.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED LATER THIS AFTERNOON...INTO
TONIGHT.

AUTEN