A persistent upper level low in west central Illinois resulted in slow moving, training thunderstorms during the afternoon and evening. 00 inch totals in Sangamon and Macon counties.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS ILX wrote it up.
A persistent upper level low in west central Illinois resulted in slow moving, training thunderstorms during the afternoon and evening. Rainfall amounts ranged from 2.00 to 4.00 inches...with isolated pockets of 5.00 inch totals in Sangamon and Macon counties.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Lincoln, IL wrote its last area forecast discussion before the first event at Sep 6, 1:11 PM CST, 2 hours 19 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 211 PM CDT SUN SEP 6 2009 .DISCUSSION... ISSUED 152 PM CDT SUN SEP 6 2009 WEAK UPPER LOW LOCATED ACRS WEST CENTRAL IL EARLY THIS AFTN WITH A WELL DEFINED DRY SLOT TO ITS EAST. MOST CONCENTRATED AREA OF SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE MAIN TROF/SHEAR AXIS ACRS SRN IL INTO KY. FURTHER NORTH...HIGH PRESSURE CONTINUES TO HOLD ACRS THE GREAT LAKES RESULTING IN A CONTINUATION OF A LIGHT EASTERLY FLOW OVR THE FORECAST AREA. MAIN FORECAST CHALLENGE THE NEXT SEVERAL DAYS WL BE WITH THE MOVEMENT OF THE UPPER WAVE AND ASSOCIATED RAIN CHANCES ALONG WITH TEMPERATURES. FURTHER OUT NEXT WEEK...MODELS INDICATING A RATHER DEEP CLOSED SYSTEM AT 500 MB TO TAKE SHAPE TO OUR NORTHWEST BRINGING IN UNSETTLED WEATHER TO THE REGION NEXT WEEKEND. SHORT TERM...TONIGHT THROUGH WEDNESDAY UPPER WAVE FCST TO EDGE SLOWLY INTO WRN INDIANA BY MONDAY AFTN WITH A SERIES OF WEAK IMPULSES ROTATING AROUND THE UPPER SYSTEM. BETTER CHANCES FOR SCATTERED SHOWERS WILL BE ACRS THE EAST TNT AND WL MAINTAIN LOW CHANCE (SCATTERED) POPS FOR MONDAY...AGAIN HIGHER POPS EAST. WITH ABUNDANT LOW LEVEL MOISTURE IN PLACE TNT...ANY DECREASE IN CLOUD COVER WILL LEAD TO SOME PATCHY DENSE FOG AFTER MIDNIGHT. MODELS INDICATING SOME WEAK INSTABILITY MONDAY AND TUESDAY AFTERNOONS AS WE MAY SEE MORE BREAKS IN THE CLOUD COVER DURING THE DAY. NAM-WRF SHOWING A WEAK SHORTWAVE ROTATING ACRS CNTRL IL CONINCIDING WITH PEAK HEATING MONDAY AFTN...WHICH MAY LEAD TO AN INCREASE IN COVERAGE OF SHOWERS AND ISOLD THUNDERSTORMS...ESP CLOSER TO THE UPPER LOW AND SHEAR AXIS OVR EASTERN IL. PRECIP WL BE MAINLY DIURNALLY DRIVEN ON MONDAY AND TUESDAY...WITH THE LOSS OF DAYTIME HEATING LATE IN THE DAY LEADING TO A DECREASE IN COVERAGE OF PRECIP. MODELS DEPICT BROAD CYCLONIC FLOW OVR THE REGION INTO MID-WEEK WHICH WILL RESULT IN A RAPID DEVELOPMENT IN CLOUDS DURING THE DAY. WITH THE UPPER SYSTEM WEAKENING WITH TIME AND VERY LITTLE IN THE WAY OF A SFC REFLECTION/BOUNDARIES...OUR PRECIP CHANCES WILL BE LIMITED TO SLGT CHANCES ACRS THE EAST...CLOSER TO THE UPPER TROF. A GRADUAL MODERATING TREND IS EXPECTED TUE AND WED AS CLOUD COVER IS EXPCTD TO BE LESS THAN TODAY...WITH AFTN HIGHS INCREASING A FEW DEGREES TOMORROW...MAINLY IN THE UPPER 70S...WITH READINGS AROUND 80 OR IN THE LOWER 80S SOUTHEAST TUE AFTN. UPPER WAVE TO SHIFT FAR ENOUGH TO OUR EAST BY MID-WEEK TO KEEP ALL OF THE FORECAST AREA DRY WITH SEASONABLY WARM TEMPS. LONG TERM...THURSDAY THROUGH SUNDAY MODELS HAVE TENDED TO SLOW DOWN OUR NEXT WEATHER MAKER FOR LATE NEXT WEEK WITH NOT MUCH FRONTAL ACTIVITY/SHOWERS EXPECTED OVR OUR AREA UNTIL AT LEAST LATE FRIDAY OR SATURDAY. COMPARED TO ABOUT 12 HOURS AGO...MODELS IN MUCH BETTER AGREEMENT WITH RESPECT TO STRENGTH AND PLACEMENT OF THE CLOSED UPPER LOW ACRS THE PLAINS STARTING LATE FRIDAY. WITH THE SLOWER SOLUTION PREFERRED...IT APPEARS OUR BEST CHANCES FOR RAIN WL HOLD OFF UNTIL FRIDAY NIGHT OR SATURDAY...24 TO 36 HOURS SLOWER THAN WHAT WE SAW YESTERDAY AT THIS TIME. ALL THE MEDIUM RANGE MODELS INDICATE A RETURN TO THE PATTERN WE EXPERIENCED ALL SUMMER LONG STARTING NEXT WEEKEND AS ANOTHER DEEP CLOSED OFF SYSTEM AT 500 MB SETS UP ACRS THE GREAT LAKES REGION BRINGING US DAMP AND COOL CONDITIONS WHILE THE HEAT RIDGE HOLDS FIRM ACRS THE WESTERN U.S. SMITH && .AVIATION... ISSUED 1245 PM CDT SUN SEP 6 2009 A 582 DM 500 MB LOW PRESSURE NEAR LINCOLN IL WILL CONTINUE ITS SLOW DRIFT EAST INTO EAST CENTRAL IL BY EVENING AND INTO WEST CENTRAL INDIANA BY MIDDAY MON (LABOR DAY) AS IT DEEPENS A BIT TO AROUND 580 DM. THIS WILL LIKELY KEEP SHOWERS AROUND INTO EARLY EVENING AND IN EASTERN IL TONIGHT AND MON MORNING ESPECIALLY BY CMI. ISOLATED THUNDERSTORMS POSSIBLE FROM IL RIVER SE UNTIL SUNSET AND STILL A RISK TONIGHT/MON MORNING IN EASTERN IL BY CMI. MVFR CEILINGS AND VISIBILITIES AT TIMES WITH DEC AND SPI CURRENTLY HAVING CEILINGS OF 1200 AND 1600 FT RESPECTIVELY. IFR CEILINGS AND VISIBILITIES POSSIBLE LATER TONIGHT UNTIL MID MORNING MON WITH LIFR A RISK AT BMI. 1030 MB HIGH PRESSURE OVER NEW ENGLAND AND RIDGING WESTWARD ACROSS THE GREAT LAKES REGION WILL MAINTAIN ENE WINDS THROUGH MON...5 TO 10 KTS BY DAY AND LIGHT AT NIGHT. HUETTL && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE LINCOLN IL 250 PM CDT SUN SEP 6 2009 ILZ027>031-036>038-040>057-061>063-066>068-071>073-071200- CASS-CHAMPAIGN-CHRISTIAN-CLARK-CLAY-COLES-CRAWFORD-CUMBERLAND- DE WITT-DOUGLAS-EDGAR-EFFINGHAM-FULTON-JASPER-KNOX-LAWRENCE-LOGAN- MACON-MARSHALL-MASON-MCLEAN-MENARD-MORGAN-MOULTRIE-PEORIA-PIATT- RICHLAND-SANGAMON-SCHUYLER-SCOTT-SHELBY-STARK-TAZEWELL-VERMILION- WOODFORD- 250 PM CDT SUN SEP 6 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL ILLINOIS...EAST CENTRAL ILLINOIS AND SOUTHEAST ILLINOIS. .DAY ONE...THIS AFTERNOON AND TONIGHT ISOLATED THUNDERSTORMS WILL OCCUR THROUGH THIS EVENING AS A DISTURBANCE IN THE UPPER ATMOSPHERE MOVES SLOWLY EASTWARD ACROSS EAST CENTRAL ILLINOIS. NO SEVERE STORMS ARE EXPECTED...HOWEVER SOME SPOTS COULD SEE LOCALLY HEAVY RAINS OF 1 TO 2 INCHES ESPECIALLY EAST OF THE ILLINOIS RIVER. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY ISOLATED THUNDERSTORMS ARE POSSIBLE MONDAY AFTERNOON UNTIL SUNSET AND AGAIN THURSDAY. THE NEXT CHANCE OF THUNDERSTORMS WILL BE FRIDAY AND SATURDAY AS A COLD FRONT MOVES SLOWLY THROUGH THE MIDWEST. AT THIS TIME THE RISK FOR SEVERE WEATHER APPEARS LOW. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT. KH
The Lincoln radar (KILX), 26 km away, was scanning. The volume nearest the first event began at 21:29 UTC.
4 flash flood. Local standard time, as filed.
Slow moving thunderstorms produced rainfall rates of 2.00 inches per hour and flash flooding in northwest Macon County. The heaviest rain was near Warrensburg where 4.00 to 5.00 inches was reported. Numerous streets and rural roads were flooded.
Slow moving thunderstorms produced rainfall rates of 2.00 inches per hour and flash flooding in northern Christian County. The heaviest rain was north of Mount Auburn, along the Sangamon River valley. where 4.00 to 5.00 inches was reported. Numerous rural roads were flooded.
Slow moving thunderstorms produced rainfall rates of 2.00 inches per hour and flash flooding in extreme eastern Sangamon County. The heaviest rain was near Illiopolis where 4.00 to 5.00 inches was reported. Numerous streets and rural roads were flooded, particularly near the Sangamon River valley.
Slow moving thunderstorms produced rainfall rates of 2.00 inches per hour and flash flooding in western and central Sangamon County, including the western suburbs of Springfield. The heaviest rain was from New Berlin to the west side of Springfield where 2.50 to 3.50 inches was reported. Numerous streets and rural roads were flooded.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2009Every state in 2009This day in weather historyWarnings in Illinois, September 2009
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 197578, 197579, 197581, 197582.