Event summary for 09/20/01:A cold front over Central Iowa, combined with a strong upper level short wave trough moving through Eastern Iowa during the evening hours, and produced a broken line of thunderstorms from Northeast Iowa, through Northeast Missouri. Wind shear and strong instability aloft, helped a few of these storms produce very large hail over Eastern Iowa.
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.
Event summary for 09/20/01:A cold front over Central Iowa, combined with a strong upper level short wave trough moving through Eastern Iowa during the evening hours, and produced a broken line of thunderstorms from Northeast Iowa, through Northeast Missouri. Wind shear and strong instability aloft, helped a few of these storms produce very large hail over Eastern Iowa. The storms produced wind and hail, as well as heavy rain. Intense rainfall fell at nearly 2 inches per hour in parts of Southeast Iowa and Northwest Illinois. This intense rain resulted in urban flooding in Stephenson County, 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 Sep 20, 1:50 PM CST, 7 hours 20 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE QUAD CITIES IA IL 250 PM CDT THU SEP 20 2001 AVN AND ETA SIMILAR IN HANDLING STRONG VORT SEEN ON W/V IMAGERY OVER EASTERN SD ATTM...AND CONTINUE TO SHEAR IT ACRS NORTHERN IA THIS EVENING...EVENTUALLY REACHING THE WI/IL BORDER BY 12Z FRI. SFC LOW REFLECTION OF UPPER SYSTEM ACRS WEST CENTRAL INTO SOUTHWEST IA AT 18Z ...BIT FURTHER SOUTHEAST OF NEW SHORT RANGE MODEL PLACEMENT. MSAS AND SFC ANALYSIS INDICATING PRESSURE FALL BULLSEYE MOVING NORTHEAST OF THE DSM AREA...WITH SFC LOW AND TRIPLE POINT LOOKING TO FOLLOW THIS EVENING. ETA AND AVN GENERALLY TAKE TRIPLE POINT ACRS SIMILAR PATHS...MOVING FROM WEST-TO-EAST JUST NORTH OF THE I-80 CORRIDOR TONIGHT...AND WITH CURRENT TRENDS PREFER MORE PROGRESSIVE AVN SPEED OF SFC SYSTEM WHICH PLACES IT ACRS FAR NORTHEAST CWA BY 06Z TONIGHT. CONVECTIVE ACTIVITY FLARING UP ACRS MN/IA BORDER WILL PROBABLY FORM INTO A SLIGHTLY ELEVATED COMPLEX THAT WILL AFFECT THE NORTHERN THIRD OF THE CWA THROUGH MIDNIGHT...WITH FCST SOUNDING PRECIPITABLE WATERS SUGGESTING LOCALLY HEAVY RAINFALL POSSIBLE WHERE MORE SUBSTANTIAL STORMS OCCUR. LAPS AND MSAS INDICATING DE-STABILIZATION CONTINUING ACRS EAST IA...INTO WEST CENTRAL IL...AND WITH BULK OF CVA WITH UPPER SYSTEM AND MAIN COLD FRONT YET TO SWEEP THROUGH... FEEL MOST OF CWA TO BE AT RISK OF ACTIVITY FOR FIRST HALF OF NIGHT. VIS LOOP INDICATED CU AND ACCAS ACRS CENTRAL AND SOUTHWEST IA SUGGEST SOME ATMOSPHERIC RECHARGE...AND ADDITIONAL SHOWERS AND STORMS SHOULD EVENTUALLY FOLLOW BEHIND ONGOING SOUTHERN CWA CONVECTION LATER TONIGHT...ESPECIALLY WITH FROPA. WOULD THINK THAT WITH MARGINAL H85 INFLOW ACRS EAST IA...AND EARLIER NOCTURNAL AFFECTS THIS TIME OF YEAR SHOULD LIMIT WIDESPREAD SEVERE THREAT BY THE TIME IT GETS HERE...BUT SOUNDINGS/WBZS STILL FAVORABLE FOR HAIL GENERATION WITH ANY SUBSTANTIAL STORM. WITH LINGERING CVA AND LLVL MOISTURE LATE TONIGHT...AREAS OF POST FRONTAL RAIN POSSIBLE INTO FRI MORNING. WILL TAKE FWC/FAN BLEND FOR LOWS TONIGHT...GENERALLY LOW TO MID 50S. SOME CLEARING TO EVENTUALLY OCCUR LATER ON FRI WITH WEAK UPPER RIDGING BUILDING ACRS BUT SOME LINGERING CLOUD COVER MAY TEMPER HIGHS A BIT AND WILL SIDE WITH MIDDLE OF ROAD MAV VALUES. WEST- NORTHWEST UPPER FLOW TO MAINLY KEEP VARIOUS VORT PIECES SHUTTLING ACRS TO THE NORTH OF THE REGION THROUGH SAT MORNING...UNTIL NEXT MAIN VORT DIGS ACRS THE UPPER MIDWEST SAT NIGHT. BRISK FRONTOGENESIS AT LOWER LEVELS ASSOCIATED WITH THIS FEATURE AND AHEAD OF INCOMING CANADIAN AIR MASS...WILL KICK UP ANOTHER ROUND OF SHOWERS AND STORMS...WITH MODELS TRENDING QUICKER WITH THIS PROCESS LAST FEW RUNS. MAY INTRODUCE CHANCE AS EARLY AS LATE SAT AFTERNOON ACRS NORTHWEST CWA...WITH BETTER POPS SAT NIGHT. LONGER RANGE(SUN-THU)...MEDIUM RANGE MODELS AGAIN IN DISAGREEMENT FOR SOME UNCERTAINTIES IN LATER PERIODS. LATEST MRF NOW HAS TRENDED TO OLD UKMET SOLUTION OF DEVELOPING LARGE CUT-OFF UPPER LOW OVER IN/IL BY LATE MON...WITH MRF PROGGING THIS COLD-CORE FEATURE TO SLOWLY GYRATE OVER THE WESTERN GRT LKS THROUGH REST OF LONG RANGE FCST PERIOD...FOR GENERALLY CLOUDY AND COOL WEEK WITH PERIODS OF LIGHT RAIN AND DRIZZLE. LATEST UKMET AND EURO ARE NOW MORE PROGRESSIVE WITH WAVE AND BRUNT OF COLD AIR SURGE FURTHER EAST ACRS EASTERN OH RVR VALLEY...AND DEVELOP CUT-OFF OVER NORTHERN APPALACHIANS ON TUE. EURO AND UKMET DO BRING STRONG LOWER AND UPPER RIDGING ACRS UPPER MS RVR VALLEY FOR MID WEEK DRY AND COOL PERIOD... AND IF DECIDE TO LEAN TOWARD UKMET/EURO GENERAL CONSENSUS...WILL STILL HAVE TO TONE DOWN TEMPS FROM TUE-THU. WILL TAKE LATE LOOK AT LATEST UKMET RUN FOR FINAL DECISION. .DVN... IA...NONE. IL...NONE. MO...NONE. JDH
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
802 PM CDT THU SEP 20 2001
TIME(CDT) .....CITY LOCATION..... STATE ...EVENT/REMARKS...
....COUNTY LOCATION....
0759 PM FARMINGTON IA HEAVY RAIN
09/20/01 VAN BUREN REPORTED BY STORM
SPOTTER. 1.30 INCHES OF
RAIN IN 45 MINUTES.PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
825 PM CDT THU SEP 20 2001
TIME(CDT) .....CITY LOCATION..... STATE ...EVENT/REMARKS...
....COUNTY LOCATION....
0820 PM 1 N KEITHSBURG IL .5 INCH HAIL
09/20/01 MERCER REPORTED BY LAW
ENFORCEMENT OFFICIAL.PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
827 PM CDT THU SEP 20 2001
TIME(CDT) .....CITY LOCATION..... STATE ...EVENT/REMARKS...
....COUNTY LOCATION....
0820 PM 1 N KEITHSBURG IL 50 MPH TSTM GUST
09/20/01 MERCER REPORTED BY LAW
ENFORCEMENT OFFICIAL.PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
925 PM CDT THU SEP 20 2001
TIME(CDT) .....CITY LOCATION..... STATE ...EVENT/REMARKS...
....COUNTY LOCATION....
0910 PM FREEPORT IL URBAN FLOODING
09/20/01 STEPHENSON ROUTE 26 NEAR REED AVE
CLOSED DUE TO STANDING
WATER.
REPORTED BY LAW
ENFORCEMENT OFFICIAL.IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007- 009-015>018-024>026-034-035-MOZ009-010-210330- SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE QUAD CITIES IA IL 931 PM CDT THU SEP 20 2001 ...SEVERE THUNDERSTORM WATCHES CANCELED... SEVERE THUNDERSTORM WATCH NUMBER 746...WHICH WAS IN EFFECT UNTIL 11 PM CDT FOR ALL OF EASTERN IOWA...AND NORTHWEST AND WEST CENTRAL ILLINOIS...HAS BEEN CANCELED. THIS INCLUDES THE FOLLOWING COUNTIES... IN IOWA...BUCHANAN...DELAWARE...DUBUQUE...BENTON...LINN...JONES... JACKSON...IOWA...JOHNSON...CEDAR...CLINTON...SCOTT...MUSCATINE... LOUISA...WASHINGTON...KEOKUK...JEFFERSON...HENRY...DES MOINES...LEE AND VAN BUREN. IN ILLINOIS...JO DAVIESS...STEPHENSON...CARROLL...WHITESIDE...ROCK ISLAND...HENRY...BUREAU...PUTNAM...MERCER...WARREN...HENDERSON... HANCOCK AND MCDONOUGH. SEVERE THUNDERSTORM WATCH NUMBER 747...WHICH WAS IN EFFECT UNTIL 11 PM CDT FOR NORTHEAST MISSOURI...HAS ALSO BEEN CANCELED. THIS INCLUDES THE FOLLOWING COUNTIES... IN MISSOURI...CLARK AND SCOTLAND. SCATTERED SHOWERS AND THUNDERSTORMS WILL BE FOUND THROUGH MIDNIGHT... MAINLY ALONG AND EAST OF THE MISSISSIPPI RIVER...AS A COLD FRONT MOVES THROUGH. ANY THUNDERSTORMS ARE EXPECTED TO REMAIN BELOW SEVERE LIMITS. THEREFORE...THE SEVERE THUNDERSTORM WATCHES HAVE BEEN CANCELED. MCCLURE
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
956 PM CDT THU SEP 20 2001
...SUMMARY OF STORM REPORTS FOR THE EVENING OF 09/20/01...
TIME(CDT) .....CITY LOCATION..... STATE ...EVENT/REMARKS...
....COUNTY LOCATION....
0545 PM KESWICK IA 1 INCH HAIL
09/20/01 KEOKUK REPORTED BY LAW
ENFORCEMENT OFFICIAL.
0628 PM LIBERTYVILLE IA .5 INCH HAIL
09/20/01 JEFFERSON REPORTED BY STORM
SPOTTER.
0739 PM 5 W MONTICELLO IA 3 INCH HAIL
09/20/01 JONES REPORTED BY PUBLIC.
0744 PM MEMPHIS MO 1 INCH HAIL
09/20/01 SCOTLAND REPORTED BY LAW
ENFORCEMENT OFFICIAL.
0750 PM 5 E MEMPHIS MO .75 INCH HAIL
09/20/01 SCOTLAND REPORTED BY STORM
SPOTTER. TORRENTIAL
RAIN AND 40 MPH WIND.
0750 PM 5 E MEMPHIS MO .75 INCH HAIL
09/20/01 SCOTLAND REPORTED BY STORM
SPOTTER.
0750 PM MEMPHIS MO 40 MPH TSTM GUST
09/20/01 SCOTLAND REPORTED BY STORM
SPOTTER.
0759 PM FARMINGTON IA HEAVY RAIN
09/20/01 VAN BUREN REPORTED BY STORM
SPOTTER. 1.30 INCHES OF
RAIN IN 45 MINUTES.
0759 PM 1 N KEITHSBURG IL .5 INCH HAIL
09/20/01 MERCER REPORTED BY LAW
ENFORCEMENT OFFICIAL.
0820 PM 1 N KEITHSBURG IL .5 INCH HAIL
09/20/01 MERCER REPORTED BY LAW
ENFORCEMENT OFFICIAL.
0820 PM 1 N KEITHSBURG IL 50 MPH TSTM GUST
09/20/01 MERCER REPORTED BY LAW
ENFORCEMENT OFFICIAL.
0910 PM FREEPORT IL URBAN FLOODING
09/20/01 STEPHENSON ROUTE 26 NEAR REED AVE
CLOSED DUE TO STANDING
WATER.
REPORTED BY LAW
ENFORCEMENT OFFICIAL.The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
Route 26 near Reed Ave in Freeport reported closed due to standing water. Reported by law enforcement.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2001Every state in 2001This day in weather historyWarnings in Illinois, September 2001
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: 5268906.