River levels remained high across central and northern Iowa especially along the West Fork of the Des Moines River. Rainfall through early to mid May caused the river to go back into flood at Emmetsburg and Humboldt for a short period in mid May.
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.
River levels remained high across central and northern Iowa especially along the West Fork of the Des Moines River. Rainfall through early to mid May caused the river to go back into flood at Emmetsburg and Humboldt for a short period in mid May.
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 12, 5:19 PM CST, 4 hours 41 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 619 PM CDT Sat May 12 2018 ...Updated for 00z Aviation Discussion... .SHORT TERM.../Tonight through Sunday/ Issued at 331 PM CDT Sat May 12 2018 Surface front remains near the Iowa/Missouri border this afternoon with extensive status field across the state. Temperatures have not budged much in most locations given the thick cloud cover and anticipate the clouds to linger through tonight as moisture trapped underneath frontal inversion remains. There continues to be extensive flow northward into the state above the frontal inversion although there is a significant cap in place, especially in southern Iowa. This weakens farther north and this is where convective development is expected late this afternoon and evening. Meanwhile, another surge of moisture and forcing will arrive from the southwest with convection spreading south and west into central and even southern Iowa by mid to late evening along the axis of the low level jet. Convection will remain well elevated with any concern for severe weather coming from hail. Mean flow should take much of the convection to the east overnight although new development on southern flank will cause overall mean movement to be southeast. Therefore, anticipate any northern convection to sink southeast into central and southeast portions of the forecast area overnight. CAMS have been consistent with taking the bulk of convection to the east after midnight although most recent output suggest backbuilding into the eastern forecast area for some time overnight and this will need to be watched. While there is some concern for heavy rainfall, the areas in the east central and south east where rain is likely to be heaviest are also some of the driest areas recently. The veering low level jet will eventually weaken convergence across the area late tonight with any lingering pcpn likely ending prior to daybreak. Still plenty of uncertainly for pcpn on Sunday as there is some suggestion for a dying convective system to enter western Iowa toward daybreak. This would affect western portions of the forecast area before dissipating although not all output is showing this scenario. Have continued some POPs in the far west and south to account for this and the front, otherwise have left most areas dry on Sunday or at least until late afternoon before another round of convection will be possible. Temperature ranges should be muted given the extensive cloudiness from tonight into Sunday and have tried to cut back on diurnal ranges despite guidances best effort to have bigger ranges. .LONG TERM.../Sunday night through Saturday/ Issued at 331 PM CDT Sat May 12 2018 Sunday evening both the Euro and GFS show a weak shortwave topping the upper ridge as a nearly stationary boundary hovers near southern Iowa. Forcing and instability increase from late in the afternoon through the evening so I expect to see an increase in shower/thunderstorm chances through the evening then pushing east overnight. Some of the stronger storms could produce a hail/wind threat but overall severe potential remains low. Monday there may be some lingering showers/storms in the morning but there will be a general lull until mid afternoon and especially Monday night and Tuesday when a stronger wave pushes across the region. The surface low and frontal boundary will...by now...have pushed further into Iowa thus widespread shower and thunderstorms will be moving across the region. Once again the lack of deep shear will keep the overall severe threat low but the models show a broad area of bulk shear from I-80 to about highway 20 so there will be at least an isolated threat for severe storms with hail and damaging wind again the main threats. Models diverge some for late Tuesday into Thursday with the Euro pushing a ridge over the Upper Midwest while the GFS has just some weak non-descript flow over the state with a low developing to the west. The GFS develops some precip late Wednesday into Thursday across far southern Iowa. It is the only model to do so. As a result, confidence is low in any precip threat during this period. I kept the slight chance PoPs going for now but this period may see little to no precip. It is the only period in the next 7 days that will be relatively dry. For late week into next weekend, the upper ridge slides east putting us in southwest flow. We will warm up and see more moisture over the region. A surface low and frontal boundary develops over the Plains and will extend into the Upper Midwest by Friday for a return to showers and thunderstorms. && .AVIATION.../For the 00Z TAFS through 00Z Sunday evening/ Issued at 619 PM CDT Sat May 12 2018 Ceilings not already in IFR will lower into this category or lower with some restrictions in visibility due to fog also expected. Showers and thunderstorms will form this evening into the early hours of Sunday with highest confidence over southern Iowa at DSM and OTM, though typical adjustments to impacts can be expected. Models indicate storms may arrive from Nebraska in the morning, but low confidence to mention at this time. While there should be improvement in visibility in the morning and later in the ceilings, left out any VFR mention late in the period for brevity. && .HYDROLOGY... Issued at 331 PM CDT Sat May 12 2018 Three flood warnings remain in effect for portions of the West Fork Des Moines and Cedar Rivers. We will continue to see periods of showers and thunderstorms through Tuesday then again later in the week with potentially locally heavy rainfall. This would impact rivers further, especially across northern Iowa. Continued monitoring of forecast conditions will be warranted. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...Cogil LONG TERM...FAB AVIATION...Ansorge HYDROLOGY...FAB
Hazardous Weather Outlook National Weather Service Des Moines IA 348 PM CDT Sat May 12 2018 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097-132100- Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo- Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun- Webster-Hamilton-Hardin-Grundy-Black Hawk-Crawford-Carroll-Greene- Boone-Story-Marshall-Tama-Audubon-Guthrie-Dallas-Polk-Jasper- Poweshiek-Cass-Adair-Madison-Warren-Marion-Mahaska-Adams-Union- Clarke-Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne- Appanoose-Davis- 348 PM CDT Sat May 12 2018 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...This afternoon and tonight Scattered thunderstorms are expected throughout the evening. Isolated storms will linger overnight across the far south. Severe storms are not expected but a few of the stronger storms could produce small hail. Locally heavy rain is also likely at times. River flood warnings remain in effect for portions of the upper reaches of the Des Moines River. Please refer to our website at weather.gov/desmoines for further details. .DAYS TWO THROUGH SEVEN...Sunday through Friday. There will be periods of thunderstorms throughout the week. The severe weather potential remains low at this time, but a few isolated severe storms cannot be ruled out. Heavy rain is possible as well and may exacerbate the river flooding. .SPOTTER INFORMATION STATEMENT... Spotter activation is not anticipated, but reports are always welcome and encouraged. FAB
The national radar mosaic for the moment the first event began.
2 flood. Local standard time, as filed.
The West Fork of the Des Moines River at Emmetsburg crested at 11.15 feet on 13 May 2018 at 14:00 UTC.
The West Fork of the Des Moines River at Humboldt crested at 10.63 feet on 16 May 2018 at 08:30 UTC.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2018Every state in 2018This day in weather historyWarnings in Iowa, May 2018
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: 755398, 755399.