An area of low pressure and associated cold front moved east through Iowa during the early morning of September 7. This brought thunderstorms, isolated areas of hail ranging from ping pong ball size to pea size, heavy rain of over 2 inches, and strong winds of 60 mph at the Cedar Rapids Airport.
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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 DVN wrote it up.
An area of low pressure and associated cold front moved east through Iowa during the early morning of September 7. This brought thunderstorms, isolated areas of hail ranging from ping pong ball size to pea size, heavy rain of over 2 inches, and strong winds of 60 mph at the Cedar Rapids Airport. Observer measured rainfall amounts ranged from 2.00 inches in Belle Plaine to nothing at Donnellson and Keokuk. Doppler radar indicated possible rainfall amounts of around 2.5 inches east of West Liberty and also northwest and south of Williamsburg, IA.
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 6, 10:53 PM CST, 2 hours 19 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE QUAD CITIES IA IL 1153 PM CDT THU SEP 6 2012 .AVIATION... SHOWERS AND THUNDERSTORMS WILL CONTINUE TO SPREAD/DEVELOP ACROSS THE TAF SITES OVERNIGHT INTO EARLY FRIDAY WITH PERIODS OF MVFR TO LOCALLY IFR VSBYS WITH THE HEAVIER PCPN. THERE COULD BE A BREAK IN THE PCPN OR AT LEAST A DECREASE IN COVERAGE FOR A WHILE FRIDAY MORNING BEFORE ANOTHER ROUND OF PCPN SPREADS BACK ACROSS MUCH OF THE AREA IN ASSOCIATION WITH UPPER JET AND SHARPENING UPPER TROUGH AXIS. THIS MAY BE MOD/HVY RAIN WITH EMBEDDED STORMS WITH MVFR TO IFR CONDITIONS. PCPN SHOULD TAPER OFF FROM NORTHWEST TO SOUTHEAST BY MID AFTERNOON THROUGH EARLY EVENING... FOLLOWED BY GRADUAL DECREASE IN CLOUDS AS DRIER AIR MOVES IN. WINDS INTO FRIDAY MORNING WILL BE FROM THE E/SE AT 4-10 KTS.... THEN SHOULD SHIFT TO N AND NW BY LATE MORNING AND AFTERNOON AS SFC LOW PASSES TO THE SOUTH. THE NORTHWEST WINDS COULD GUST 15-20 KTS DURING THE AFTERNOON ESPECIALLY AT KCID AND KDBQ. && .PREV DISCUSSION... /ISSUED 1000 PM CDT THU SEP 6 2012/ UPDATE... THUNDERSTORMS HAVE DEVELOPED WITHIN THE PAST HR OR SO OVER NORTHWEST IA. PROPAGATION VECTORS FROM THE W/NW COUPLED WITH NW TO SE ORIENTATION OF MOISTURE AND INSTABILITY GRADIENTS SUGGESTS ACTIVITY TO SLIDE E/SE OVERNIGHT. AS RESULT... HAVE MADE ADJUSTMENTS TO POPS PLACING HIGHEST POPS IN THE W/SW SECTIONS OF CWA (FOR MAINLY AFT 07Z-08Z) AND LOWEST POPS E/NE CWA. SEVERE THREAT MINIMAL AND CONFINED TO HAIL WITH INVERSION NEAR 850 MB PER 00Z DVN RAOB... WITH BETTER ELEVATED INSTABILITY AND LOW LEVEL MOISTURE SUPPORTING SOUTHEAST IA FOR LOW RISK OF MARGINALLY SEVERE HAIL. OTHERWISE... LOWERED MINS A FEW DEGS IN MANY AREAS WITH TEMPS AT 02Z WITHIN 3-5 DEGS OF LOWS SEVERAL PLACES... AND WITH WINDS STILL FAIRLY LIGHT AND SKIES MAINLY CLEAR TO PTCLDY FOR NEXT FEW HOURS. QUICK NOTE... SOME OF THE NEW 00Z MODEL GUIDANCE SUGGESTS THAT COULD SEE MORE WIDESPREAD AND HEAVIER ROUND OF PCPN FRI LATE AM THROUGH AFTN COINCIDENT WITH FAIRLY ROBUST SYNOPTIC SCALE LIFT IN FORM OF RRQ OF UPPER JET AND SHARPENING UPPER TROUGH. WOULD NEED TO ADJUST POPS TO RAISE INTO AFTN AND ALSO INCREASE QPF FOR PORTIONS OF CWA... IN ADDITIONS TEMPS WOULD NEED LOWERING AND COULD STAY IN THE 60S IN A LOT OF PLACES. THIS COUPLED WITH NORTHERLY WINDS MAKING FOR A FALLISH FEEL. MCCLURE PREV DISCUSSION... /ISSUED 304 PM CDT THU SEP 6 2012/ SYNOPSIS... WEAK HIGH PRESSURE OVER THE AREA PROVIDING SUNNY SKIES AND LIGHT WINDS WITH CURRENT TEMPERATURES IN THE UPPER 70S TO LOWER 80S. SURFACE DEW POINTS HAVE FALLEN INTO THE UPPER 40S AT SOME LOCATIONS IN THE CWA. HOWEVER DEEPER MOISTURE NOT FAR AWAY WITH 850 MB DEW POINT AT KTOP AT 12Z/06 OF 16C. WARM ADVECTION CONTINUED TO TRIGGER A LINE OF SEVERE STORMS MOVING EASTWARD ACROSS THE OZARKS. OTHER STORMS WERE LOCATED IN WESTERN MN NEAR A WARM FRONT AND MID LEVEL SPEED MAX. PRESSURE FALLS WERE OCCURRING OVER A BROAD AREA OF THE PLAINS AND INTO THE UPPER MIDWEST. HAASE SHORT TERM...TONIGHT AND FRIDAY... FORECAST FOCUS ON BENEFICIAL RAIN EVENT WITH WIDESPREAD 1/2 TO 1.5 INCH RAIN AMOUNTS...POSSIBLY UP TO 2 INCHES AT SOME LOCATIONS. TONIGHT...SPC HAS MUCH OF EASTERN IOWA INTO WESTERN ILLINOIS IN A SLIGHT RISK FOR SEVERE STORMS AFTER MIDNIGHT TONIGHT INTO EARLY FRIDAY MORNING. FORECAST SOUNDINGS INDICATE ELEVATED INSTABILITY WITH FREEZING LEVELS ABOUT 13K FT. ALONG WITH STRONG THETA-E ADVECTION INTO THE AREA. THE CWA WILL ALSO BE ON THE NOSE OF A 40 KNOT SOUTHWESTERLY LOW LEVEL JET WITH STRONG LOW LEVEL CONVERGENCE. THIS SUPPORTS AT LEAST A 1 INCH HAIL THREAT AND POTENTIALLY LOCAL DAMAGING WIND GUSTS. PRECIPITABLE WATERS INCREASE TO OVER 1.50 INCHES SO HEAVY RAINS WILL BE LIKELY WITH THE STRONGER STORMS. STILL EXPECT MANY LOCATIONS TO PICK UP 1/2 TO 1 INCH OF RAIN BY MORNING...LOCALLY HIGHER AMOUNTS POSSIBLE. WILL CARRY A SMALL CHANCE POP IN OUR WESTERN COUNTIES LATE THIS EVENING BUT POPS WILL BE INCREASED TO AT LEAST 80 PERCENT AFTER MIDNIGHT FOR MUCH OF THE CWA. MINIMUM TEMPERATURES WILL BE IN THE LOWER TO MID 60S AS WINDS TURN SOUTHEAST AND CLOUDS INCREASE. FRIDAY...RAIN AND EMBEDDED THUNDERSTORMS EXPECTED FOR MUCH OF THE MORNING HOURS...THEN TAPERING OFF DURING THE AFTERNOON IN THE NORTHWEST CWA. THE RAIN SHOULD CONTINUE IN OUR SOUTHEAST CWA MUCH OF THE DAY. ADDITIONAL RAIN OF UP TO AN INCH BY THE TIME THE RAIN COMES TO AN END BY FRIDAY EVENING. WITH THE CLOUD COVER AND WIDESPREAD RAIN TEMPERATURES WILL BE AT LEAST 10 DEGREES COOLER COMPARED TO TODAY. WILL FORECAST MAX TEMPS ONLY IN THE UPPER 60S ALONG HIGHWAY 20 TO THE MID 70S IN OUR FAR SOUTHERN CWA. WILL HAVE HIGH POPS FOR MUCH OF THE DAY EXCEPT IN OUR NORTHWEST WHERE WE WILL LOWER TO CHANCE POPS IN THE AFTERNOON. HAASE LONG TERM...FRIDAY NIGHT THROUGH NEXT THURSDAY... THE UPPER TROF WILL BE MOVING THROUGH THE CWFA FRIDAY EVENING WITH THE BEST FORCING AND LOW AND MID LEVEL MOISTURE EAST OF THE CWFA BY 00Z. SOME LOW POPS ARE STILL WARRANTED EAST OF THE MISSISSIPPI RIVER AFTER 00Z BUT THE RAIN THREAT SHOULD END BY MID EVENING. FOR THE REST OF SATURDAY NIGHT EXPECT CLEARING SKIES WITH LOW LEVEL CAA. EXPECT LOWS TO DROP INTO THE MID OR UPPER 40S NW BY SATURDAY MORNING AND WITH LOW 50S SOUTHEAST. SATURDAY AND SUNDAY HIGH PRESSURE WILL MOVE EAST OUT OF THE PLAINS AND THROUGH THE MISSISSIPPI VALLEY. FOR THE MOST PART THE HIGH WILL BRING DRY WEATHER AND BELOW NORMAL TEMPERATURES FOR THE WEEKEND. THERE IS SOME QUESTION THOUGH SATURDAY NIGHT OVER THE NORTHEASTERN CWFA. THE ECMWF CONTINUES TO DROP A S/W SOUTH THROUGH THE WESTERN GREAT LAKES PRODUCING SOME -SHRA OVER WI AND NE IL WITH THE WESTERN FRINGE OF PRECIP SHIELD CLOSE TO NW IL. SINCE THE ECMWF IS AN OUTLIER WITH THIS FEATURE...I/LL CONTINUE WITH A DRY FORECAST. HIGH TEMPERATURES SATURDAY SHOULD BE MAINLY IN THE LOW 70S...BUT SOME OF THE NORTHERN COUNTIES COULD STRUGGLE TO REACH THE 70 MARK. LOWS IN THE UPPER 40S AND LOW 50S ARE EXPECTED SATURDAY NIGHT...PROVIDED THE WESTERN GREAT LAKES S/W TRACKS TO NE OF THE CWFA. SUNDAY SHOULD SEE HIGHS IN THE 70S WITH THE SURFACE RIDGE MOVING EAST OF THE CWFA. FOR THE REST OF NEXT WEEK...THE LONG RANGE MODELS ARE IN GOOD AGREEMENT BRINGING ANOTHER TROF INTO THE CENTRAL U.S. BY THURSDAY. THE REGION SHOULD SEE A GOOD WARM UP MONDAY AND TUESDAY WITH THE INCREASING SOUTHERLY FLOW AHEAD OF THE COLD FRONT. TUESDAY LOOKS LIKE THE WARMEST DAY OF THE WEEK BENEFITING FROM THE RETURN FLOW AND LACK OF CLOUDS. HIGHS IN THE LOW TO MID 80S LOOK REASONABLE WITH FORECAST SOUNDINGS SHOWING AN ELEVATED WARM LAYER CAPPING OFF DEEPER MIXING. WEDNESDAY INCREASING CLOUDS AHEAD OF THE SYSTEM SHOULD LIMIT HIGHS TO THE UPPER 70S/LOW 80S. BOTH THE GFS/ECMWF ARE NOW SUGGESTING THERE WILL BE SOME MOISTURE RETURN AHEAD OF THE SYSTEM AND ARE GENERATING MORE QPF THAN PREVIOUS RUNS SUGGESTED WEDNESDAY NIGHT AND THURSDAY...SO LOW CHANCE POPS LOOK REASONABLE AT THIS POINT. DLF && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE QUAD CITIES IA IL 324 PM CDT THU SEP 6 2012 IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007- 009-015>018-024>026-034-035-MOZ009-010-072030- BUCHANAN-DELAWARE-DUBUQUE-BENTON-LINN-JONES-JACKSON-IOWA-JOHNSON- CEDAR-CLINTON-MUSCATINE-SCOTT-KEOKUK-WASHINGTON-LOUISA-JEFFERSON- HENRY IA-DES MOINES-VAN BUREN-LEE-JO DAVIESS-STEPHENSON-CARROLL- WHITESIDE-ROCK ISLAND-HENRY IL-BUREAU-PUTNAM-MERCER-HENDERSON- WARREN-HANCOCK-MCDONOUGH-SCOTLAND-CLARK- 324 PM CDT THU SEP 6 2012 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...THIS AFTERNOON AND TONIGHT THE STORM PREDICTION CENTER HAS A SLIGHT RISK FOR SEVERE THUNDERSTORMS ACROSS MUCH OF EASTERN IOWA AND WESTERN ILLINOIS AFTER MIDNIGHT TONIGHT INTO EARLY FRIDAY MORNING. THE MAIN THREAT WILL BE HAIL AT LEAST AS LARGE AS A QUARTER. LOCALLY DAMAGING WIND GUSTS ARE ALSO POSSIBLE. HEAVY RAIN IS LIKELY IN THE STRONGER STORMS AND SOME LOCATIONS MAY SEE AMOUNTS OVER ONE INCH. .DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY RAIN WITH EMBEDDED THUNDERSTORMS WILL CONTINUE ACROSS MUCH OF THE OUTLOOK AREA ON FRIDAY. THE THUNDERSTORMS WILL BE MORE PREVALENT ALONG AND SOUTH OF INTERSTATE 80. SEVERE WEATHER IS NOT ANTICIPATED... BUT SOME LOCATIONS MAY SEE ADDITIONAL RAINFALL AMOUNTS UP TO AN INCH BY THE TIME THE RAIN ENDS BY FRIDAY EVENING. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED LATER TONIGHT INTO EARLY FRIDAY MORNING. REPORTS OF RAINFALL AMOUNTS OF MORE THAN AN INCH WILL BE APPRECIATED TONIGHT AND FRIDAY. HAASE
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE QUAD CITIES IA IL 106 AM CDT FRI SEP 7 2012 IAZ063-064-070700- IOWA-JOHNSON- 106 AM CDT FRI SEP 7 2012 ...STRONG THUNDERSTORM... AT 102 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM NEAR PARNELL...OR 14 MILES SOUTHEAST OF MARENGO...MOVING EAST AT 35 MPH. * THE THUNDERSTORM WILL BE NEAR... 6 MILES SOUTH OF TIFFIN AROUND 125 AM CDT... CORALVILLE AND OAKDALE AROUND 130 AM CDT... UNIVERSITY HEIGHTS...IOWA CITY AND HILLS AROUND 135 AM CDT... ONE HALF INCH DIAMETER HAIL AND BRIEF HEAVY RAIN...IS EXPECTED WITH THIS STORM. EXPECT PONDING OF WATER ON ROADS AND IN LOW-LYING AREAS. LAT...LON 4175 9137 4154 9138 4156 9201 4167 9203 TIME...MOT...LOC 0605Z 267DEG 31KT 4161 9190 08
The Quad Cities radar (KDVN), 79 km away, was scanning. The volume nearest the first event began at 07:10 UTC.
6 hail, 2 thunderstorm wind, 1 lightning. Local standard time, as filed.
Quarter sized hail fell about 2 miles south southeast of Hills, IA at 212 am CDT September 7.
A 60 mph wind gust was measured by the ASOS at the Cedar Rapids Municipal Airport at 320 am CDT September 7.
Wind gusts estimated to be 65 mph blew down a 12 foot fruit tree about 9 miles east southeast of Columbus Junction, IA.
Nickel sized hail fell covering the ground in Grandview, IA at 328 am CDT September 7.
Ping Pong ball sized hail fell in Millersburg, IA at 355 am CDT September 7.
Lightning struck the bell tower atop the College Hall building at Cornell College in Mount Vernon, IA around 4 am CDT September 7. Damage was confined to the bell tower and part of the attic.
Quarter sized hail fell in Parnell, IA at 403 am CDT September 7.
Quarter sized hail fell about 1 mile north of Thornburg, IA around 417 am CDT September 7.
Nickel sized hail fell in Grandview, IA at 515 am CDT September 7.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2012Every state in 2012This day in weather historyWarnings in Iowa, September 2012
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: 409599, 409600, 409613, 409602, 409605, 409607, 409608, 409609, 409610.