Hail and Damaging Winds in Illinois, August 3, 2003

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
255 PM CDT SUN AUG 3 2003

LATEST SURFACE ANALYSIS HAD LOW CENTERED OVER EXTREME SOUTHWEST LAKE
MICHIGAN...WITH NUMEROUS TROFS AND BOUNDARIES EVIDENT ACROSS THE
GREAT LAKES AND MIDWEST (MOST PIVOTING AROUND LOW...OTHERS
CONVECTIVE OR LAKE BREEZE IN ORIGIN). MAIN CONCERN THROUGH THE SHORT
TERM CONTINUES TO BE THE THREAT OF SHOWERS AND THUNDERSTORMS.

12Z MODELS IN REASONABLE AGREEMENT WITH RESPECT TO FEATURES EXPECTED
TO IMPACT CENTRAL ILLINOIS. HOWEVER...FAVOR THE ETA SOLUTION WITH
THE SHORT WAVE TUESDAY AND TUESDAY NIGHT OVER THE MORE AGGRESSIVE
GFS. GUIDANCE TEMPERATURES CLOSE AND REASONABLE...SO WILL NOT STRAY
TOO FAR.

TONIGHT THROUGH MONDAY NIGHT...IN SUMMARY...THIS PERIOD WILL WIND UP
MUCH LIKE THE PAST FEW DAYS THOUGH WITH GRADUALLY IMPROVING
CONDITIONS (REDUCED THREAT OF SHOWERS/STORMS). SHOWERS AND
THUNDERSTORMS EXPECTED AREAWIDE THIS EVENING WITH DIURNAL
INSTABILITY INTERACTING WITH YET ANOTHER SHORTWAVE AROUND UPPER LOW
OVER THE GREAT LAKES REGION. THE UPPER LOW SHIFTS A BIT TO THE SOUTH
AND EAST FOR MONDAY AND MONDAY NIGHT AND THERE IS NOT ANOTHER
SIGNIFICANT WAVE PROGGED TO ROTATE AROUND IT AT THIS TIME. STILL...
DIURNAL HEATING (WITH COLD POOL ALOFT STILL NEARBY) AND WEAK
CYCLONIC FLOW WARRANT LEAVING A CHANCE OF SHOWERS/STORMS IN THE
FORECAST (ESPECIALLY OVER THE EASTERN CWA) THOUGH COVERAGE SHOULD BE
LOW.

TUESDAY AND TUESDAY NIGHT...UPPER LOW PULLS FAR ENOUGH EAST OF
CENTRAL ILLINOIS THAT ATTENTION TURNS WELL UPSTREAM FOR THE FIRST
TIME IN A FEW DAYS. A SHORT WAVE IS PROGGED TO SLIDE DOWN THE MEAN
WESTERN U.S. RIDGE INTO THE MID MISSISSIPPI VALLEY. WHILE MOST OF
THE UPPER FORCING IS PROGGED TO STAY SOUTH AND WEST OF THE FORECAST
AREA...WAA/ISENTROPIC ASCENT ON THE FRONT END OF THE WAVE MAY THROW
SOME PRECIPITATION NORTH INTO FORECAST AREA. WILL RAISE POPS
SLIGHTLY IN GRIDDED FORECAST TO MATCH BETTER WITH SURROUNDING
OFFICES...BUT LEAVE MENTION OUT OF THE WORDED FORECAST AT THIS TIME.
IT SEEMS THAT THE GFS IS TOO AGGRESSIVE WITH ITS QPF WITH THIS
FEATURE.

WEDNESDAY...A WEAK SHORT WAVE IS PROGGED TO SLIDE SOUTH SOUTHEAST
THROUGH ILLINOIS...WITH MODEL SOUNDINGS SUGGESTING ENOUGH
INSTABILITY PRESENT BY AFTERNOON TO CONTINUE WITH A CHANCE OF
SHOWERS/STORMS.

THURSDAY THROUGH SUNDAY...MODEL/ENSEMBLE AGREEMENT PRETTY GOOD THAT
A RIDGE WEST/TROF EAST PATTERN WILL PERSIST ACROSS NORTH AMERICA FOR
THE FORESEEABLE FUTURE. CENTRAL ILLINOIS WILL BE LOCATED IN THE
NORTHWEST FLOW ON THE FRONT OF THE RIDGE/BACK OF THE TROF AND WILL
CONTINUE TO SEE TEMPERATURES AT OR SLIGHTLY BELOW NORMAL THROUGH THE
PERIOD. WHILE SHOWERS/STORMS CAN NOT BE RULED OUT ANY DAY FROM
EITHER COLD POOL/TROFFING WITH THE UPPER LOW OR AN UNFORESEEN
SHORTWAVE RIDING DOWN THE UPPER RIDGE...CHANCES ARE TOO LOW TO
MENTION AT THE MOMENT.

.ILX...NONE.

BAK

ILZ027>031-036>038-040>057-061>063-066>068-071>073-041100-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LINCOLN IL
130 PM CDT SUN AUG 3 2003

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

.DAY ONE...TODAY AND TONIGHT

THERE IS A RISK FOR SEVERE THUNDERSTORMS ACROSS CENTRAL AND
SOUTHEAST ILLINOIS THIS AFTERNOON AND TONIGHT. A SURFACE BOUNDARY
COMBINED WITH AN UPPER LEVEL DISTURBANCE WILL IGNITE SCATTERED
THUNDERSTORMS ONCE AGAIN. THE PRIMARY THREAT WITH ANY STORMS
THAT DEVELOP THIS AFTERNOON AND TONIGHT WILL BE LARGE
HAIL...DAMAGING WINDS...HEAVY RAINFALL AND TORNADOES.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

WIDELY SCATTERED THUNDERSTORMS ARE EXPECTED OVER CENTRAL AND
SOUTHEAST ILLINOIS ON MONDAY. AT THIS TIME...NO ORGANIZED SEVERE
WEATHER THREAT IS ANTICIPATED ON MONDAY. THE NEXT CHANCE FOR
THUNDERSTORMS WILL BE LATE TUESDAY INTO WEDNESDAY AS A FRONTAL
SYSTEM APPROACHES CENTRAL ILLINOIS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY ONCE AGAIN BE REQUIRED THIS AFTERNOON AND
TONIGHT. THE BEST AREA FOR ORGANIZED SEVERE WEATHER WILL BE ALONG
AND EAST OF INTERSTATE 55. ALSO...THE BEST TIME FOR SEVERE WEATHER
WILL BE MAINLY FROM 200 PM TO 1000 PM.

&&
THIS PRODUCT...ALONG WITH OTHER WEATHER...HYDROLOGIC
AND CLIMATE INFORMATION...IS AVAILABLE ON THE WEB AT:

HTTP://WWW.CRH.NOAA.GOV/ILX. THIS ADDRESS IS ALL
IN LOWER CASE.

EH