Mid to late May rainfall across portions of northeast Iowa kept soil moisture high and river levels generally elevated. Heavier rainfalls around the Waterloo area and to the north, including portions of the Cedar River basin, overnight on the 27th into the morning of the 28th allowed the Cedar River to reach flood stage for just over 24 hours from 0045 UTC on the 30th to 0315 UTC on the 31st.
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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 DMX wrote it up.
Mid to late May rainfall across portions of northeast Iowa kept soil moisture high and river levels generally elevated. Heavier rainfalls around the Waterloo area and to the north, including portions of the Cedar River basin, overnight on the 27th into the morning of the 28th allowed the Cedar River to reach flood stage for just over 24 hours from 0045 UTC on the 30th to 0315 UTC on the 31st.
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 29, 5:15 PM CST, 1 hour 30 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 615 PM CDT Fri May 29 2020 ...Updated for 00z Aviation Discussion... .DISCUSSION.../Tonight through Friday/ Issued at 300 PM CDT Fri May 29 2020 High pressure will move into Iowa tonight keeping clear skies and cool temperatures in place. The high will shift east on Saturday and a weak disturbance aloft will graze southwest Iowa. This will bring a chance for light showers mainly to the southwest but there will be little impact with QPF amounts of a tenth of an inch or less. Still for those with outdoor plans, you should be prepared for a brief shower. Sunday the surface high slips further east with upper level riding pushing in from the west. Another shortwave will top the ridge and drop across Iowa Sunday night through Monday morning. There will be some instability in place so shower and a few thunderstorms are possible during this time. The severe threat is low during this time and again QPF amounts will be light so impacts to rivers will be minimal. As the upper ridge strengthens and build into the state Tuesday the heat and humidity will increase substantially. 40 degree dewpoints will be 60+ degree dewpoints and temperatures will be will into the 80s with lower 90s even possible. A decent shortwave is still on tap to flatten the ridge Tuesday night and Wednesday. During this time a surface low will develop over the Central Plains and a frontal boundary will stretch across the region though models vary as to the location of the front with the Euro pushing a cold front across Iowa and the GFS now lifts a warm front north into MN with a cold front back into the Plains. Northern Iowa to perhaps southern MN and back west appear to be the most likely areas to see precip during this time. If the GFS is correct, then the aforementioned cold front will drag across the state on Wednesday, prolonging the precip chances. If the Euro is correct, Wednesday will be dry. Thursday into Thursday night, both models build high pressure back into the region for a dry and warmer period. Friday and Friday night are unclear as the Euro builds the ridge back across the region and has a disturbance riding the ridge into MN with the GFS has a big system out west pushing the upper ridge east and allowing several shortwave to ride up the backside of the ridge impacting western/northern Iowa. It's unclear how this will play out on day 7 so I went with a model blend of PoPs which frankly look a little on the high side for now but there will likely be several iterations of the models so it's best not to flip flop that far out. && .AVIATION.../For the 00Z TAFS through 00Z Saturday evening/ Issued at 613 PM CDT Fri May 29 2020 High confidence in VFR TAFs throughout forecast period. There may be showers nearing KDSM and KFOD Saturday afternoon, but at this time, it appears they will remain west of these airports. Thunder chances are very low to nil. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && DISCUSSION...FAB AVIATION...Kotenberg
Hazardous Weather Outlook National Weather Service Des Moines IA 249 PM CDT Fri May 29 2020 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097-302000- 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- 249 PM CDT Fri May 29 2020 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...This afternoon and tonight No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Saturday through Thursday A few non-severe thunderstorms are possible Sunday night and early Monday morning. Periodic thunderstorm chances are in the forecast Tuesday night through Friday. The severe weather and heavy rain threats will be better determined in the coming days. .SPOTTER INFORMATION STATEMENT... Spotters are not expected to be needed through at least early next week. FAB
The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
The Cedar River at Cedar Falls crested at 89.44 feet on May 30th at 1215 UTC or 615am CST.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2020Every state in 2020This day in weather historyWarnings in Iowa, May 2020
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: 896802.