Thunderstorms developed along a boundary in West Central Illinois during the afternoon hours. Favorable winds aloft allowed two storms to briefly pulse up to severe limits and produce damaging winds in Monmouth, Illinois and southwest of Macomb, Illinois.
Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
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 DVN wrote it up.
Thunderstorms developed along a boundary in West Central Illinois during the afternoon hours. Favorable winds aloft allowed two storms to briefly pulse up to severe limits and produce damaging winds in Monmouth, Illinois and southwest of Macomb, Illinois.
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 Quad Cities, IA wrote its last area forecast discussion before the first event at Aug 11, 2:42 AM CST, 9 hours 58 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE QUAD CITIES IA IL 342 AM CDT MON AUG 11 2003 SHORT TERM FORECAST CHALLENGE IS POPS TODAY AS VORT LOBES ROTATING AROUND OHIO VALLEY UPPER LOW IMPACT AREA. WATER VAPOR IMAGERY SHOWS VORT MAX PUSHING INTO EAST CENTRAL IA THAT HAS IGNITED SHOWERS AND FEW TSRA OVER SOUTH CENTRAL IA ALONG BOUNDARY LEFT OVER FROM TSRA COMPLEX AT EDGE OF MAIN MID LEVEL LOBE NOW PUSHING INTO SOUTHEAST KS. HAVE PLACE ISOLATED WORDING FOR MORNING TO ACCOUNT FOR THIS ACTIVITY ALONG FAR SOUTHWEST CWA BORDER...WHICH SHOULD END AROUND SUNRISE. NEXT UPSTREAM SHORTWAVE SEEN MOVING INTO NORTHERN MN AND LAKE SUPERIOR REACHES NORTHERN CWA BY 00Z. THIS TIMING WILL BRING BEST TSRA CHANCES TO MAINLY AREAS SOUTH OF I-80...WHERE ASSOCIATED CVA WILL ARRIVE DURING PEAK HEATING. EXPECTED COVERAGE IN LINE WITH LOWER GUIDANCE VALUES OF 30 PERCENT. REDUCED AREAS TO NORTH TO 20 PERCENT WITH CHANCES KEPT IN MORNING FOR ANY LINGERING SHOWERS THAT MAY DRIFT IN FROM SOUTHERN WI OVERNIGHT CONVECTION. OHIO VALLEY UPPER LOW RETROGRADES SOUTHWEST TO TX BY MID WEEK WITH UPPER RIDGE SHEARING NORTHEAST INTO NORTHERN PLAINS. HIGH DEVELOPING OVER GREAT LAKES RESULTS IN DEEP NORTHEAST TO EAST LOW LEVEL FLOW OVER FORECAST AREA TUESDAY AND WEDNESDAY. MODERATE AFTERNOON INSTABILITY...COMBINED WITH VORT MAX IN MID LEVEL NORTHEAST FLOW AND H85 MOISTURE GRADIENT SHOULD LEAD TO CONVECTION ALONG LAKE BOUNDARY TUESDAY...WHICH MAY DRIFT SOUTHWEST ACROSS FAR SOUTHEAST ZONES LATE AFTERNOON INTO EARLY EVENING AND THUS INTRODUCED ISOLATED POPS THERE. SIMILAR SITUATION WEDNESDAY...BUT WITH WEAKER MID LEVEL FORCING...LEFT OUT OF GRIDS AND ZONES FOR NOW. BY END OF WEEK...UPPER RIDGE WILL BE NEARLY OVERHEAD TO SUPPORT HIGHS BACK IN UPPER 80S. MEDIUM RANGE GUIDANCE SUGGESTS STRONG SHORTWAVE TO FLATTEN RIDGE OVER WEEKEND...BUT SIGNIFICANT TIMING DIFFERENCES REMAIN. REMOVED FRIDAY POPS...BUT KEPT POPS THROUGH WEEKEND WITH SUNDAY STILL LOOKING TO HAVE BEST CHANCE OF MUCH NEEDED RAIN. .DVN... IA...NONE. IL...NONE. MO...NONE. SHEETS
IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007- 009-015>018-024>026-034-035-MOZ009-010-121100- HAZARDOUS WEATHER OUTLOOK...CORRECTED WORDING NATIONAL WEATHER SERVICE QUAD CITIES IA IL 449 AM CDT MON AUG 11 2003 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EASTERN IOWA... NORTHWEST AND WEST CENTRAL ILLINOIS...AND NORTHEAST MISSOURI. .DAY ONE...TODAY AND TONIGHT SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS AFTERNOON. THESE THUNDERSTORMS ARE NOT EXPECTED TO BECOME SEVERE. AN UPPER LEVEL DISTURBANCE MOVING SOUTH ACROSS THE AREA WILL TRIGGER SHOWERS AND THUNDERSTORMS WITH THE GREATEST CHANCES SOUTH OF INTERSTATE 80 AFTER 3 PM. THE MAIN THREAT FROM THUNDERSTORMS TODAY WILL BE CLOUD TO GROUND LIGHTNING AND LOCALLY HEAVY DOWNPOURS DUE TO SLOW STORM MOVEMENT. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED. && MORE INFORMATION MAY BE OBTAINED AT THE FOLLOWING INTERNET WEB SITE: HTTP://WWW.CRH.NOAA.GOV/DVN (ALL LOWER CASE) SHEETS
The Lincoln radar (KILX), 122 km away, was scanning. The volume nearest the first event began at 18:39 UTC.
2 thunderstorm wind, 1 lightning. Local standard time, as filed.
Huge maple tree down
Tree uprooted
Tree struck and fell onto 2 garages
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2003Every state in 2003This day in weather historyWarnings in Illinois, August 2003
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: 5374189, 5374190, 5374191.