During the early morning hours of May 2nd a strong disturbance lifting northward centered the development of a line of thunderstorms along a warm front bisecting Iowa from west to east. As this line of thunderstorms moved eastward into eastern Iowa, it produced sporadic straightline wind and microburst damage in Benton, Iowa, Muscatine, and Jackson Counties.
Every event with a place to put it. 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.
During the early morning hours of May 2nd a strong disturbance lifting northward centered the development of a line of thunderstorms along a warm front bisecting Iowa from west to east. As this line of thunderstorms moved eastward into eastern Iowa, it produced sporadic straightline wind and microburst damage in Benton, Iowa, Muscatine, and Jackson Counties. Pea to penny sized hail was also reported with this line of thunderstorms.
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 May 1, 11:52 PM CST, 2 hours 23 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE QUAD CITIES IA IL 1252 AM CDT WED MAY 2 2012 .AVIATION... SOME LINGERING LOW MVFR TO EVEN IFR DECKS STILL PERSISTING IN VCNTY OF DBQ...BUT OTHERWISE VFR CIGS WITH SCTRD ELEVATED SHOWERS AND SOME THUNDERSTORMS DEVELOPING IN VCNTY OF CID AND DBQ. SOUTHEAST SFC WINDS AROUND 8-12 KTS SHOULD LIMIT FOG...BUT STILL SOME POCKETS OF 3-5SM UNDER LINGERING CLOUD DECK/NORTH OF WARM FRONT THROUGH 09Z. WITH 40+ KT SOUTH TO SOUTHWESTERLY FLOW AT 2K FT AGL...LOW LEVEL WIND SHEAR HAS BEEN ADDED TO THE TAFS THROUGH ERLY WED MORNING. MORE NUMEROUS SHOWERS AND THUNDERSTORMS WILL MOVE IN FROM THE WEST AND IMPACT ALL TERMINALS BESIDES MAYBE BRL AFTER 08Z THROUGH 14Z BEFORE MOVING ON TO THE EAST. CHANCE OF STRONG STORMS DEVELOPING IN THE VCNTY OF CID AND DBQ LATE IN THE TAF CYCLE. OTHERWISE MUCH OF WED MAY BE VFR AFTER MID MORNING WITH BRISK SOUTH TO SOUTHWEST SFC WINDS OF 13-16 KTS SUSTAINED AND GUSTS OVER 20 KTS. ..12.. && .PREV DISCUSSION... /ISSUED 329 PM CDT TUE MAY 1 2012/ SYNOPSIS... MCV STARTING TO PULL EAST FINALLY...WITH THE BACK EDGE OF THE RAIN FROM THE QUAD CITIES SOUTH THROUGH MACOMB AT 20Z. THE MCV HAS HELPED HOLD THE WARM FRONT AT BAY SO FAR TODAY. BY MID AFTERNOON THE FRONT EXTENDED SSE FROM LOW PRESSURE IN SOUTH DAKOTA THROUGH CENTRAL IA THEN TURNING EAST THROUGH NORTHEAST MO INTO IL. THE MORNING UA ANALYSIS SHOWED A BROAD REGION OF SWLY MID LEVEL FLOW OVER THE WESTERN AND CENTRAL U.S. AT H8 LEE SIDE TROUGHING WAS OCCURRING OVER THE CENTRAL AND NORTHERN PLAINS. SOUTHERLY FLOW AHEAD OF THE TROF WAS PULLING WARM AND MOISTURE RICH AIR NORTH WITH A LARGE AREA OF 10-14C H8 DEWPOINTS OVER THE CENTRAL PLAINS THIS MORNING. SHORT TERM...TONIGHT AND WEDNESDAY... THE MCV WILL CONTINUE EAST AND WILL KEEP A LOW CHANCE FOR RAINSHOWERS GOING IN THE EXTREME EAST TO COVER FOR ANY LINGERING PCPN EARLY THIS EVENING. THE ATTENTION THEN TURNS TO TSRA THREAT ASSOCIATED WITH NORTHERN PLAINS SURFACE LOW AND THE ASSOCIATED COLD FRONT EXTENDING SW FROM THE LOW AND ALSO ALONG THE WARM FRONT AS IT LIFTS NORTH TONIGHT. OTHER THAN THE LOW POPS FOR THE DEPARTING MCV HAVE KEPT THE EARLY EVENING DRY FOR THE ENTIRE AREA. AFTER MID EVENING WENT WITH LOW POPS THROUGH MIDNIGHT TO COVER POSSIBLE TSRA DEVELOPMENT ALONG THE WARM FRONT AS IT LIFTS NORTH AND TO COVER ANY TIMING ISSUES WITH TSRA EXPECTED TO MOVE IN FROM THE NORTHWEST OVERNIGHT. THE MAIN THUNDERTORM EVENT FOR THE CWA WILL BE AFTER MIDNIGHT. AN MCS IS EXPECTED TO DEVELOP THIS EVENING OVER EASTERN SD AND MOVE SOUTHEAST. MODELS SUGGEST THE MCS SHOULD REACH THE NORTHWEST COUNTIES OF THE FORECAST AREA JUST AFTER MIDNIGHT AND SHOULD SPREAD OVER THE AREA DURING THE EARLY MORNING HOURS. WENT WITH LIKELY POPS NORTH AFTER MIDNIGHT AND CHANCE POPS IN THE SOUTH SINCE THE TSRA WILL BE MOVING INTO WARMER MID LEVEL TEMPS OVER SOUTHERN IA AND NRN MO LATE TONIGHT. THE SYSTEM WILL LIKELY BE WEAKENING AS IT MOVES INTO THE CWFA SO THERE IS A LOW THREAT OF SEVERE STORMS FEATURING LARGE HAIL AND DAMAGING WIND GUSTS AS THE MAIN THREAT. WITH WARMER AIR SPREADING OVER THE AREA TONIGHT OVERNIGHT WILL LIKELY OCCUR DURING THE EVENING AND SHOULD BE MAINLY IN THE UPPER 50S AND LOW 60S. WEDNESDAY THE REGION WILL BE IN THE WARM SECTOR WITH THE WARM FRONT STALLED TO OUR NORTH. ANY LINGERING CLOUDS FROM THE OVERNIGHT MCS SHOULD THIN BY THE AFTERNOON. SOME SUN ALONG WITH SOUTH WINDS SHOULD BOOST TEMPS INTO THE 80S. WENT WITH CHANCE POPS NORTH NEAR THE SURFACE BOUNDARY AND SLIGHT CHANCE SOUTH WHERE THE AIRMASS SHOULD BE CAPPED BUT WHERE LINGERING SURFACE BOUNDARIES MAY EXIST FROM THE OVERNIGHT CONVECTION. ..DLF.. LONG TERM...WEDNESDAY NIGHT THROUGH NEXT TUESDAY NON-LINEAR PROCESSES WILL BE DOMINATING THE SENSIBLE WX WITH THE POTENTIAL FOR SEVERAL MCS EPISODES. SINCE NON-LINEAR PROCESSES ARE DOMINATE...THERE IS A POTENTIAL FOR SIGNIFICANT DEVIATIONS FROM FORECASTED TEMPERATURES AND RAINFALL DEPENDING UPON WHERE OUTFLOW BOUNDARIES ARE LOCATED. PWATS ABOVE 1.25 INCHES INDICATE THE POTENTIAL FOR HEAVY RAIN ESPECIALLY IF TRAINING OF STORMS CAN OCCUR. WHAT OCCURS DURING THE DAY WEDNESDAY WILL PLAY SIGNIFICANTLY INTO WEDNESDAY NIGHT/THURSDAY. MCS AND LIFT TOOLS ARE SUGGESTING THAT AN MCS WILL EITHER DEVELOP ACROSS NORTHERN IOWA LATE WED AFTERNOON/EVENING OR ACROSS THE NORTHERN CWFA. THE FIRST SCENARIO SEEMS MORE REASONABLE AS THE BETTER LLJ WILL BE WEST OF THE AREA AS IS THE MOISTURE TRANSPORT. HOWEVER...DIURNAL CONVECTION IS POSSIBLE ACROSS THE CWFA DURING THE EVENING THAT COULD MERGE WITH THE MCS THAT DEVELOPS IN NORTHERN IOWA. CORFIDI VECTORS SUGGEST A GENERAL EAST NORTHEAST MOVEMENT WITH SLOW DEVELOPMENT TO THE SOUTH. THE MODELS ARE SUGGESTING THE POTENTIAL FOR THE BACK BUILDING OF CONVECTION WEDNESDAY NIGHT. SO...DEPENDING UPON WHERE THE MCS DEVELOPS THERE MAY BE A POTENTIAL FOR SEVERE STORMS WED EVENING BEFORE THE MCS EVOLVES INTO A HEAVY RAIN EVENT. IF SEVERE STORMS DEVELOP...IT APPEARS THAT THE NORTHERN HALF OF THE CWFA WOULD BE MORE FAVORED. LIKEWISE...THE NORTHERN HALF OF THE CWFA...IF THE INTERNAL SIGNALS FROM THE MODELS ARE CORRECT... ESPECIALLY THE ECMWF...WOULD BE MORE FAVORED FOR HEAVY RAIN. A DECAYING MCS WITH OUTFLOW BOUNDARIES AND POSSIBLY A COLD POOL WILL BE OVER THE CWFA DURING THE MORNING HOURS ON THURSDAY. THESE BOUNDARIES COMBINED WITH DIFFERENTIAL HEATING WILL DETERMINE WHERE STORMS RE-DEVELOP DURING THE AFTERNOON HOURS. LATE THURS AFTERNOON/EVENING IT APPEARS THAT ANOTHER MCS WILL DEVELOP ESSENTIALLY OVER THE CWFA. SEVERE STORMS MAY AGAIN OCCUR WITH THE MCS BEFORE IT EVOLVES INTO ANOTHER MODERATE TO HEAVY RAIN EVENT. THE HEAVY RAIN THURSDAY NIGHT COULD BE OVER THE SOUTHEAST TWO THIRDS OF THE CWFA. THE MCS THAT DEVELOPS THURSDAY NIGHT WILL BE IN A DECAYING MODE FRIDAY MORNING. AGAIN...OUTFLOW BOUNDARIES AND DIFFERENTIAL HEATING WILL BE THE KEY TO WHERE STORMS DEVELOP FRIDAY AFTERNOON. FRIDAY NIGHT ON... MODEL CONSENSUS CARRIES MAINLY CHC POPS FROM FRIDAY NIGHT THROUGH NEXT TUESDAY. THE MODELS SHOW THE FRONT VACILLATING ACROSS THE AREA HELPING TO KEEP THE RAIN CHANCES GOING IN AN ACTIVE PATTERN. HOWEVER...MCS ACTIVITY MAY ACTUALLY HELP PUSH THE FRONT SOUTH OF THE CWFA AND ALLOW ONE OR POSSIBLY TWO DAYS OF DRY WX. ..08.. HYDROLOGY... SINCE APRIL 27TH RAINFALL HAS BEEN WIDELY VARIED ACROSS THE AREA. A ROUGHLY 30-40 MILE WIDE BAND OF 1 TO JUST OVER 2 INCHES OF RAIN HAS FALLEN FROM SOUTH OF ROCKFORD IL TO NORTH OF OTTUMWA IA. OUTSIDE OF THIS BAND RAINFALL HAS BEEN TWO THIRDS OF AN INCH OR LESS. AREA RIVERS HAVE SEEN LITTLE OR NO RISES FROM THE RAIN INDICATING HOW DRY IT HAS BEEN OF LATE. AN ACTIVE WEATHER PATTERN IS EXPECTED OVER THE NEXT 7 DAYS WITH SEVERAL CHANCES FOR RAIN THAT MAY BE HEAVY. SINCE MOST OF THIS RAIN WILL LIKELY OCCUR DUE TO THUNDERSTORM ACTIVITY...COMPUTER MODELS ARE HIGHLY VARIED ON WHERE AND HOW MUCH RAIN WILL OCCUR. MOST COMPUTER MODELS GENERALLY AGREE THAT SEVERAL INCHES OF RAIN MAY BE POSSIBLE THROUGH NEXT TUESDAY. THE FIRST ROUND OF POTENTIALLY HEAVY RAIN WILL OCCUR TONIGHT INTO WEDNESDAY MORNING. DEPENDING UPON RAINFALL AMOUNTS AND WHERE IT FALLS...THERE IS A REASONABLY GOOD CHANCE OF ONLY MINOR RESPONSES FROM AREA RIVERS. SUBSEQUENT RAIN EVENTS STARTING WEDNESDAY NIGHT WILL BECOME MORE IMPORTANT AND WILL INCREASE THE CHANCES FOR MORE SIGNIFICANT RISES DEVELOPING ON AREA RIVERS. STOFLET && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE QUAD CITIES IA IL 432 AM CDT TUE MAY 1 2012 IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007- 009-015>018-024>026-034-035-MOZ009-010-020945- 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- 432 AM CDT TUE MAY 1 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...TODAY AND TONIGHT TODAY...AREAS OF SHOWERS AND EMBEDDED THUNDERSTORMS ARE POSSIBLE. ANY STORMS WILL NOT BE SEVERE. TONIGHT...THUNDERSTORMS WILL REDEVELOP THIS EVENING AND OVERNIGHT. SOME STORMS MAY REACH SEVERE LEVELS WITH LARGE HAIL UP TO THE SIZE OF GOLF BALLS THE PRIMARY RISK. TRAINING OF THUNDERSTORMS COMBINED WITH HIGH MOISTURE LEVELS MAY ALSO PRODUCE LOCALLY HEAVY RAINFALL UP TO AND POSSIBLY IN EXCESS OF 2 INCHES. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY WEDNESDAY...THE STORM PREDICTION CENTER HAS PLACED A SLIGHT RISK FOR SEVERE STORMS OVER MOST OF THE OUTLOOK AREA. THIS POTENTIAL WILL BE GREATEST NORTH OF HIGHWAY 30 IN THE LATE AFTERNOON THROUGH EVENING HOURS. THE PRIMARY SEVERE WEATHER THREAT WILL BE DAMAGING WIND AND LARGE HAIL...WITH AN ISOLATED TORNADO POSSIBLE. THURSDAY THROUGH SATURDAY...THERE WILL BE A CHANCE OF THUNDERSTORMS EACH DAY AS A FRONTAL BOUNDARY LINGERS IN THE AREA. SEVERE WEATHER WILL BE POSSIBLE...ESPECIALLY THURSDAY AND FRIDAY. THUNDERSTORMS WILL ALSO BRING A THREAT OF HEAVY RAIN AND POSSIBLE FLASH FLOODING. RAINFALL TOTALS FROM WEDNESDAY THROUGH FRIDAY MAY EXCEED 3 INCHES...ESPECIALLY IN LOCATIONS THAT EXPERIENCE SEVERAL ROUNDS OF THUNDERSTORMS WITH HEAVY RAIN. THE EXTENDED PERIOD OF RAIN MAY ALSO LEAD TO RIVER FLOODING BY THE WEEKEND INTO EARLY NEXT WEEK. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED TODAY BUT MAY BE POSSIBLE TONIGHT. NICHOLS/SHEETS
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE QUAD CITIES IA IL 250 AM CDT WED MAY 2 2012 IAZ040-041-051-052-063-064-076-077-087-021000- BUCHANAN-DELAWARE-BENTON-LINN-IOWA-JOHNSON-KEOKUK-WASHINGTON- JEFFERSON- INCLUDING THE CITIES OF...INDEPENDENCE...MANCHESTER...VINTON... CEDAR RAPIDS...MARENGO...IOWA CITY...SIGOURNEY...WASHINGTON... FAIRFIELD 250 AM CDT WED MAY 2 2012 ...THUNDERSTORMS WITH GUSTY WINDS THROUGH 5 AM... AN AREA OF SLOWLY WEAKENING THUNDERSTORMS WILL MOVE ACROSS THE REGION THE NEXT COUPLE OF HOURS. THE STRONGEST STORMS MAY PRODUCE GUSTY WINDS OF 30 TO 40 MPH ALONG WITH A PERIOD OF HEAVY RAINFALL. SOME SMALL HAIL MAY ALSO BE POSSIBLE. LOW LYING LOCATIONS MAY ALSO EXPERIENCE FOR A SHORT PERIOD SOME PONDING OF WATER WITH ANY HEAVY RAINFALL RATES. MOST LOCATIONS WILL RECEIVE RAIN AMOUNTS BETWEEN .25 TO .75 INCHES WITH ISOLATED AMOUNTS OVER 1 INCH IN THE STRONGEST STORMS. ANY LOOSE ITEMS MAY BE BLOWN ABOUT IN THE GUSTY WINDS. NICHOLS
The Des Moines radar (KDMX), 130 km away, was scanning. The volume nearest the first event began at 08:17 UTC.
6 thunderstorm wind, 3 hail. Local standard time, as filed.
A microburst blew most of the roof off a house and some of the windows out. Three large trees were snapped. The door and roof of a machine shed and other outbuildings were damaged.
A person from the public reported shingles blown off of a house along with several trees blown down. An old silo as well as silage wagons also blew over.
The Emergency Manager reported a large tree blown over near the intersection of 51st Street and 32nd Avenue, roof blow off of a barn, and 1 grain bin was blown out. Time of the event was estimated from radar.
The largest hailstones that fell were dime sized.
Time of the event was estimated from radar.
Time of the event was estimated from radar.
A trained spotter reported several branches down about 6 inches in diameter. The time of the event was estimated from radar.
The Emergency Manager for Jackson County reported that a few 2 inch tree limbs were down in the city of Bellevue. The time of the event was estimated from radar.
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, May 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: 378312, 384051, 384052, 378300, 378301, 378303, 378316, 378314, 378315.