An unseasonably strong upper level storm system initiated scattered thunderstorms along a surface boundary across northern Illinois in a semi-dry to semi-moist atmosphere. Due to low freezing levels the storms produced copious amounts on non-severe hail.
Every event with a place to put it; 3 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.
An unseasonably strong upper level storm system initiated scattered thunderstorms along a surface boundary across northern Illinois in a semi-dry to semi-moist atmosphere. Due to low freezing levels the storms produced copious amounts on non-severe hail. The combination of the surface boundary and redevelopment allowed storms to train across the same area producing locally heavy rainfall. One lone storm pulsed severe in southeast Stephenson County and produced quarter size hail.
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 Sep 4, 9:30 AM CST, 2 hours earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE QUAD CITIES IA IL 1030 AM CDT MON SEP 4 2006 .UPDATE... UPDATED GRIDS SENT WITHIN THE LAST HOUR TO REMOVE FOG ADIVSORY AND ADJUST POPS FOR ONGOING PCPN IN THE SOUTH. ALSO UPPED TEMPS SOME IN NW IL WHERE 15Z READINGS WERE ALREADY APPROACHING FCST MAX TEMPS. OTHERWISE...PREVIOUS FORECAST IS ON TRACK AS STACKED UPPER LOW OVER CENTRAL IA HEADS SE TODAY. BASED ON 12Z KDVN SOUNDING...LOW 70S WILL BE THE MAGIC NUMBER FOR SURFACE BASED CONVECTION. AS IT STANDS NOW IT LOOKS LIKE MORNING CLOUDS AND RAIN WILL KEEP TEMPS FROM REACHING LOW 70S OVER MOST AREAS WEST OF THE RIVER. EAST OF THE RIVER BREAKS IN THE CLOUDS WERE ALLOWING TEMPS TO WARM NICELY...SO THIS WILL BE THE AREA TO WATCH THIS AFTERNOON. IF A SEVERE THUNDERSTORMS DO MATERIALIZE...THEN LARGE HAIL WILL BE PRIMARY THREAT. EARLY MORNING HWO HAS THIS NICELY OUTLINED SO NO CHANGES NEEDED THERE. ...DLF... .PREVIOUS DISCUSSION... .SYNOPSIS... CLOSED UPPER LEVEL SYSTEM OVER SW IA MOVING SLOWLY EAST SOUTHEAST AT 10 TO 15 MPH. SYSTEM PRODUCING AREA OF SHOWERS AND SOME STORMS WITH NEXT BATCH OF PRECIPITATION ALONG LEADING EDGE OF UPPER VORT LOBE FROM NEAR IOWA CITY BACK TO EAST OF OMAHA. MOVEMENT SUGGESTS THIS PRECIPITATION TO MOVE INTO FORECAST AREA FOR AT LEAST NEXT 6 TO 8 HOURS...MAINLY ALONG AND SOUTH OF HIGHWAY 30. PRESSURE FALLS ALSO SUGGEST INCREASING COVERAGE OF SHOWERS AND SOME STORMS NEXT SEVERAL HOURS WITH MAX FALLS IN CENTRAL IA MOVING INTO AREA WITH PRECIPITATION. RIBBON OF DENSE FOG ALONG MISSISSIPPI RIVER DEVELOPED IN CLEAR SLOT WITH VISIBILITIES WELL BELOW 1/4 MILE RESULTING IN A DENSE FOG ADVISORY UNTIL 8 AM UNTIL WESTERN CLOUDS AND PRECIPITATION ARRIVES. && .SHORT TERM...TONIGHT AND LABOR DAY(MONDAY)...BLEND OF NOWCAST TOOLS ABOVE AND MODELS SUGGEST KEEPING LIKELY POPS WITH HIGHEST AMOUNTS AND COVERAGE SOUTH AND EASTERN SECTIONS. CURRENT COVERAGE OF POPS HANDLED REASONABLY WELL BY ALL SOLUTIONS AT 07Z AND WENT WITH BLEND OF GFS/UKMET BASED ON LATEST TRENDS BUT ALL SOLUTIONS SIMILAR WITH MOST FAVORED AND STRONGEST FORCING SOUTHEAST. HEATING TODAY BY PM SHOULD SEE SOME STRONGER STORMS DEVELOP WITH SOME PEA TO HALF INCH HAIL POSSIBLE IF GET ENOUGH SUNSHINE FROM BREAKS IN CLOUDS FOR TEMPS TO REACH LOWER 70S WITH HIGHEST RISK SE 1/3 OR SOUTH OF A PRINCETON TO KEOSAUQUA LINE. STORM PREDICTION CENTER HAS MOST AREA IN SLIGHT RISK TODAY. HAIL RISK DUE TO LOWER WBZ OF AOB 9K AGL BUT WITH VERY LIMITED INSTABILITY OF CAPE AOB 600 J/KG AND WEAK SHEAR...SUPPORTS ISOLATED STORMS AT MOST ATTM. TEMPS LIKE YESTERDAY A CHALLENGE DEPENDING ON CLOUDS AND AMOUNT OF PRECIPITATION...KEPT UPPER 60S NW WITH LOWER 70S SE SECTIONS. WOULDN/T BE SURPRISED TO SEE SOME FOG LINGER TIL LATE AM SOME LOCATIONS DUE TO MOISTURE CONVERGENCE AND THICK CLOUDS AND NEARLY CALM WINDS. TONIGHT...HIGHEST POPS EAST AS UPPER LOW SLOWLY SLIDES EAST WITH HIGH CHANCE EAST AND LOW WEST WITH MOST ACTIVITY ENDING BY LATE EVENING DUE TO LOSS OF HEATING. TEMPS ON HIGH SIDE AND MAY STILL BE A FEW DEGREES TOO LOW WHERE CLOUDS ARE THICKEST. PATCHY FOG AGAIN POSSIBLE BUT NOT A FAVORABLE AS TONIGHT AS NORTH WINDS OF 5 MPH TO LOCALLY HIGHER SHOULD LIMIT COVERAGE. DAY SHIFT CAN REASSESS THIS. .LONG TERM...TUESDAY THROUGH WEDNESDAY... CURRENT PACKAGE REMAINS REASONABLE AND MADE ONLY MINOR CHANGES WITH SOME DAYTIME HEATING TO ALLOW FOR POPCORN SHOWERS AND POSSIBLY ISOLATED STORMS AND KEPT CHANCE POPS. UPPED MAX TEMPS A FEW DEGREES AS UPPER LOW SLIDES SOUTHEAST...DECENT SUBSIDENCE SHOULD ALLOW FOR SOME SUNSHINE TO BOOST TEMPS A FEW DEGREES AND ALSO ENHANCE POPCORN SHOWERS/STORMS AS CONVECTIVE TEMPS REACHED. KEPT SLIGHT CHANCE SE SECTIONS IN EVENING AND TRENDED TOWARD CLEARING SKIES AND LOWER TEMPS AT NIGHT. WEDNESDAY NEAR SEASONABLE WITH UPPER 70S TO AROUND 80 FOR HIGHS AND SOME DAYTIME CUMULUS CLOUDS. QUIET WEDNESDAY NIGHT WITH SFC RIDGE NEARBY KEEPING MIN TEMPS IN 50S OR NEAR SEASONAL LEVELS FOR MORE ENJOYABLE SEPTEMBER WEATHER. NO CHANGES BEYOND DAY THREE WITH ALL SOLUTIONS CONTINUING TO SUGGEST ACTIVE WEATHER FOR WEEKEND. ..NICHOLS.. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...DENSE FOG ADVISORY UNTIL 8 AM ALONG MISSISSIPPI RIVER VALLEY. IL...DENSE FOG ADVISORY UNTIL 8 AM ALONG MISSISSIPPI RIVER VALLEY. MO...DENSE FOG ADVISORY UNTIL 8 AM CLARK COUNTY. && NICHOLS
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE QUAD CITIES IA IL 515 AM CDT MON SEP 4 2006 IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007- 009-015>018-024>026-034-035-MOZ009-010-051000- BENTON IA-BUCHANAN IA-BUREAU IL-CARROLL IL-CEDAR IA-CLARK MO-CLINTON IA-DELAWARE IA-DES MOINES IA-DUBUQUE IA-HANCOCK IL-HENDERSON IL-HENRY IA-HENRY IL-IOWA IA-JACKSON IA-JEFFERSON IA-JO DAVIESS IL-JOHNSON IA- JONES IA-KEOKUK IA-LEE IA-LINN IA-LOUISA IA-MCDONOUGH IL-MERCER IL- MUSCATINE IA-PUTNAM IL-ROCK ISLAND IL-SCOTLAND MO-SCOTT IA- STEPHENSON IL-VAN BUREN IA-WARREN IL-WASHINGTON IA-WHITESIDE IL- 515 AM CDT MON SEP 4 2006 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL ILLINOIS...NORTHWEST ILLINOIS...WEST CENTRAL ILLINOIS...EAST CENTRAL IOWA...NORTHEAST IOWA...SOUTHEAST IOWA AND NORTHEAST MISSOURI. .DAY ONE...TODAY AND TONIGHT AREAS OF FOG...LOCALLY DENSE WITH VISIBILITIES REDUCED TO A FEW HUNDRED FEET WILL GRADUALLY DISSIPATE BY MID MORNING. A DENSE FOG ADVISORY REMAINS IN EFFECT FOR AREAS ALONG THE MISSISSIPPI RIVER VALLEY UNTIL 9 AM. SHOWERS AND SCATTERED THUNDERSTORMS WILL OCCUR AS AN UPPER LEVEL LOW OVER IOWA GRADUALLY MOVES EAST TODAY. IF TEMPERATURES REACH THE LOWER 70S...A FEW OF THE STORMS MAY BECOME STRONG...POSSIBLY BRIEFLY APPROACHING SEVERE LEVELS BETWEEN 1 AND 6 PM. THE GREATEST THREAT WILL BE FROM PEA TO HALF INCH HAIL WITH ISOLATED PENNY SIZED HAIL POSSIBLE. LOCATIONS MOST AT RISK FOR STRONGER STORMS WILL BE ALONG AND SOUTHEAST OF A PRINCETON ILLINOIS TO FAIRFIELD IOWA LINE. THE STORM PREDICTION CENTER HAS A SLIGHT RISK FOR LOCATIONS EAST OF A MANCHESTER IOWA TO IOWA CITY TO MACOMB ILLINOIS LINE. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY FRIDAY THROUGH SUNDAY...A FRONTAL SYSTEM WILL MOVE INTO THE REGION FRIDAY WITH A SURFACE DISTURBANCE DEVELOPING ON THE FRONT AND MOVING INTO PORTIONS OF THE MIDWEST THIS WEEKEND. THIS WILL RESULT IN AREAS OF SHOWERS AND THUNDERSTORMS. CONDITIONS REMAIN TOO UNCERTAIN TO ASSESS ANY SEVERE OR HEAVY RAIN RISK AT THIS TIME. INTERESTED INDIVIDUALS SHOULD MONITOR THIS PRODUCT FOR FURTHER UPDATES. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE POSSIBLE THIS AFTERNOON SOUTHEAST OF A PRINCETON ILLINOIS TO FAIRFIELD IOWA LINE. NICHOLS
The Quad Cities radar (KDVN), 89 km away, was scanning. The volume nearest the first event began at 19:16 UTC.
3 heavy rain, 1 hail. Local standard time, as filed.
The co-op observer reported 1.25 inches of rain in the past hour.
A spotter reported heavy rain causing some minor street flooding.
The sheriff department reported some minor small stream flooding across the eastern half of the county.
A spotter reported quarter size hail.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2006Every state in 2006This day in weather historyWarnings in Illinois, September 2006
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: 5534091, 5534092, 5534093, 5534094.