The frontal boundary from Nebraska moved into western Iowa during the evening hours. The airmass was unstable, but not overly so.
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 DMX wrote it up.
The frontal boundary from Nebraska moved into western Iowa during the evening hours. The airmass was unstable, but not overly so. CAPE values were around 1500 J/kg with Lifted Indices around -2. There was about 45 kts of effective shear in place. A few thunderstorms developed ahead of the boundary with one of the cells becoming severe. The first tornado occurred in Calhoun County at 2358 UTC where the tornado dropped into a farm field between York ave and Zearing Ave south of 320th St. about 2 miles north of Farnhamville. The tornado was an F1 tornado as it crossed the intersection of Zearing and 320th St. IT destroyed dome outbuildings north of the intersection and continued moving northeast toward Slifer in Webster County. The tornado remained on the ground crossing the Calhoun/Webster County line crossing County Road D46 between Zebulon Ave and County Road P29. The tornado destroyed three grain bins and just missed a farm. Debris was tossed over several hundred yards before the tornado weakened and lifted for the first time prior to reaching Slifer. The F1 tornado was on the ground for about 4 miles during this time with F1 strength and a width of 50 to 100 yards. The tornado was reported on the ground very intermittently from this point on with numerous reports southwest of Callender, northeast through the Woodman Hol State preserve and into the Brushy Creek State Reserve. At this point, the tornado lifted. The parent storm continued into Hamilton County. A brief touchdown was reported in Hamilton County north of Blairsburg. No damage was reported and the tornado roped out quickly.
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 Des Moines, IA wrote its last area forecast discussion before the first event at May 18, 2:45 PM CST, 3 hours 13 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 345 PM CDT WED MAY 18 2005 .DISCUSSION... TWO MAIN PROBLEM AREAS IN FORECAST...THOSE BEING CONVECTION POTENTIAL THIS EVENING THEN AGAIN SATURDAY AND SUNDAY. OVERALL MODEL/FORECAST TRENDS WERE TO WARM TEMPS A BIT MORE THE NEXT COUPLE DAYS...SHIFT UPPER LOW A BIT MORE TO THE EAST THURSDAY...AND SPEED FRONTAL TIMING SATURDAY NIGHT/SUNDAY MORNING. IN THE SHORT TERM...MAIN SURFACE LOW OVER ND WITH SFC FRONT EXTENDING SE TO NEAR THE MO RIVER. MAIN CONCERN IS WHETHER OR NOT CONVECTION WILL FIRE ALONG THIS FRONT FURTHER S AND W INTO IA. CURRENT CONVECTION OVER THE EASTERN CWA UNDER AREA OF STEEPER MID LEVEL LAPSE RATES...GOOD MOISTURE TRANSPORT AND THETA-E ADVECTION. THIS SHOULD CONTINUE TO PROGRESS TO THE EAST LATE THIS AFTERNOON AND EARLY EVENING. FURTHER WEST...BEST LOW LEVEL CONVERGENCE NOW ACROSS THE FSD AND OAX PORTIONS OF IOWA IN ASSOCIATION WITH FRONT ENTERING THE AREA. THERE IS A NARROW AXIS OF INSTABILITY AHEAD OF THE FRONT WITH LITTLE CAPPING OVER THE NW. MU CAPES NOT THAT IMPRESSIVE AND GENERALLY AOB 1000J/KG. WITH SOME SUPPORT...WILL HAVE TO KEEP CHANCE POPS IN THE WEST THIS EVENING. LOW LEVEL CONVERGENCE DECREASES LATER THIS EVENING AS BOUNDARY LOSES IT PUSH. IF STORM DO FORM...DEEP LAYERED SHEER WOULD SUPPORT SOME ELEVATED ROTATING UPDRAFTS CAPABLE OF SEVERE HAIL. ON THURSDAY...MODELS ARE MORE IN AGREEMENT THAT THE UPPER LOW WILL PASS EAST OF THE CWA AND MOVE A BIT SLOWER TO THE SOUTH. GFS STILL PRODUCES THE BEST CHANCE OF AFTERNOON INSTABILITY SHOWERS/TSRA IN ASSOCIATION WITH THE MID LEVEL COLD POOL. HAVE SHIFTED POPS A BIT FURTHER EAST AND DECREASED THEM A BIT BUT WILL STILL MAINTAIN LOW CHANCE OVER THE EAST. WITH THE UPPER LOW FURTHER EAST AND SLOW...IT DOES ALLOW THE AREA TO WARM A BIT MORE THAN PREVIOUSLY FORECAST AS A GOOD DOWNSLOPE COMPONENT TO THE LOW LEVEL FLOW WILL PERSIST INTO THE EARLY AFTERNOON. IN THE LONGER TERM...MODELS ARE FASTER WITH THE FRONTAL MOVEMENT SATURDAY NIGHT. NAM IS QUITE STRONG WITH THE LOW LEVEL JET AND ASSOCIATED THETA-E ADVECTION LATE FRIDAY NIGHT AND SATURDAY MORNING OVER NW IA. GFS MUCH WEAKER WITH THE RETURN FLOW. HAVE BROUGHT POPS INTO THE SATURDAY PERIOD WITH POTENTIAL ELEVATED WARM AIR ADVECTION PCPN AND FASTER FRONTAL MOVEMENT. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE && JAW
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DES MOINES IA 348 PM CDT WED MAY 18 2005 IAZ004>007-015>017-023>025-033>035-044>046-057-058-070-071-081- 092-192100- EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO- POCAHONTAS-HUMBOLDT-WRIGHT-SAC-CALHOUN-WEBSTER-CRAWFORD-CARROLL- GREENE-AUDUBON-GUTHRIE-CASS-ADAIR-ADAMS-TAYLOR- 348 PM CDT WED MAY 18 2005 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WEST CENTRAL AND NORTH CENTRAL IOWA. .DAY ONE...TONIGHT SCATTERED THUNDERSTORMS ARE FORECAST ACROSS THE OUTLOOK AREA THIS EVENING. A FEW STORMS MAY BECOME SEVERE DURING THE EVENING WITH THE MAIN THREAT FROM LARGE HAIL. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY THERE ARE ADDITIONAL THREATS OF THUNDERSTORMS ON SATURDAY INTO EARLY SUNDAY THEN AGAIN NEXT TUESDAY. AT THIS TIME...SEVERE WEATHER APPEARS MARGINAL THIS WEEKEND AS WELL AS NEXT TUESDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVIATION MAY BE NEEDED THIS EVENING. IAZ026>028-036>039-047>050-059>062-072>075-082>086-093>097-192100- FRANKLIN-BUTLER-BREMER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-BOONE- STORY-MARSHALL-TAMA-DALLAS-POLK-JASPER-POWESHIEK-MADISON-WARREN- MARION-MAHASKA-UNION-CLARKE-LUCAS-MONROE-WAPELLO-RINGGOLD-DECATUR- WAYNE-APPANOOSE-DAVIS- 348 PM CDT WED MAY 18 2005 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA. .DAY ONE...TONIGHT WIDELY SCATTERED THUNDERSTORMS ARE POSSIBLE THIS EVENING...HOWEVER NO SEVERE WEATHER IS EXPECTED. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY THERE ARE ADDITIONAL THREATS OF THUNDERSTORMS ON SATURDAY INTO EARLY SUNDAY THEN AGAIN NEXT TUESDAY. AT THIS TIME...SEVERE WEATHER APPEARS MARGINAL THIS WEEKEND AS WELL AS NEXT TUESDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.
The national radar mosaic for the moment the first event began.
3 tornado. Local standard time, as filed.
Tornado touched down on a farm north of Farnhamville, damaging several buildings on the farm. The tornado moved from Calhoun County into Webster County.
Tornado moved from Calhoun County into Webster County. It moved through mostly open country and have a very intermittent track from Slifer on northeast. Damage occurred to several grain bins, then tornado lifted for some time with another tornado forming over Hamilton County.
Tornado occurred north of Blairsburg with only a bried touchdown.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2005Every state in 2005This day in weather historyThe tornado archive for Iowa, 2005Warnings in Iowa, May 2005
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: 5446456, 5446454, 5446455.