A boundary lifting north through Iowa was the focus for convection and tornado development. Sufficient instability and enhanced shear near the boundary helped produce seven tornadoes on this day.
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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.
A boundary lifting north through Iowa was the focus for convection and tornado development. Sufficient instability and enhanced shear near the boundary helped produce seven tornadoes on this day. One tornado occurred in Waukee, Iowa but produced only EF0 damage. The strongest tornado was an EF1 located south of Eagle Grove reaching a width of almost 250 yards.
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 26, 11:46 AM CST, 32 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 1246 PM CDT Tue May 26 2020 .DISCUSSION.../Today through Monday/ Issued at 420 AM CDT Tue May 26 2020 Summary... Wet and stormy conditions will continue over the next couple of days, with the best opportunity for strong to severe storms later today. Of growing concern may be hydrologic issues with the potential for additional periods of moderate to heavy rainfall in areas that have already received around 2 to 4 inches over the last 48 hours. Drier and cooler conditions will move in at the end of the week, though a few showers/storms may scoot through Saturday into Sunday. Today and Tonight... While it is a different day, the story appears to remain relatively the same with another round of storms associated with a surface low and associated MCV riding northward within the mean flow. As such, we will also have another opportunity for strong to severe storms by the afternoon and evening. Initial wave of storms this morning should remain sub-severe with current widespread convection/precip limiting organization within a marginally supportive environment. Environment becomes more supportive by the afternoon though as the surface low approaches NE/IA/MO border areas including, MUCAPE values 1500-2000 J/kg, roughly 30-40 kts 0-3km and 0-6km shear, 150- 200 m2/s2 SRH, 0-3km CAPE around 100 J/kg, backing low level winds resulting in better veering hodographs of varying degrees (model of choice dependent), etc... All in all, not a slam dunk for severe, but given recent results, another fair setup for some low level turning/stretching resulting in the SPC 5% tor threat. Cannot rule out other severe modes, but suggestions are that long lived organization may be difficult to come by to achieve severe hail or prolonged wind threats. On top of that, moderate to heavy rainfall will also be a threat once again with PWats remaining around 1.50 to 1.75 inches with the sustained Gulf moisture stream. With antecedent conditions being on the wet side across much of southern and central IA, river and overland flooding risks do increase. Fortunately, this system will be progressive and will not setup the wettest areas of the state for prolonged training storms. Another 1 to 2+ inches may be possible, but believe southern and central Iowa can handle it without much consequence. As such, have shied away from a flood watch, though western and southern neighbors have done so. Northwest IA where surface boundary will set up will also be of concern for heavy rainfall, but those areas have only seen around an inch to inch and a half or less over the last 2 days, setting them up to handle additional rainfall well. WPC has a slight risk for excessive rainfall along the MN/IA border, which makes sense with the potential for heaviest rainfall/longer training of storms into MN versus IA. Wednesday through Thursday... Additional storms will be likely as the upper level trough cuts off and meanders in the TX/OK/AR/LA region for a couple of days before becoming absorbed into the broader flow. As that occurs, portions of Iowa will see a lingering surface boundary that will act as a focus for continued shower/storm activity. With Gulf moisture remaining, expect conditions to remain quite wet. SW and C Iowa will likely need to be monitored for flooding threats though, as well as other portions of the state as heavy rainfall threat area continues to be honed in. Obviously boundary location will play a major role as to which areas will see the most rain within this time frame, and best estimates right now are roughly the southeast half of the state. Friday through Monday... As the cutoff upper level low fills in NW flow will prevail, yielding drier and cooler conditions Friday. While the cooler conditions will continue, the dry conditions may not as synoptic guidance is in fair agreement of a shortwave moving through Saturday into Sunday producing a few shower chances. Expect temperatures to fall back into upper 60s to lower 70s through the weekend before rising back into the 80s early next week as ridging returns. && .AVIATION.../For the 18Z TAFS through 18Z Wednesday afternoon/ Issued at 1246 PM CDT Tue May 26 2020 Numerous showers and embedded thunderstorms are expected this afternoon into the early evening across central Iowa. Anticipate MVFR to IFR conditions in and around the thunderstorms with southeast winds in most locations. Lower ceilings and areas of light fog are expected late tonight with MVFR to IFR ceilings, especially along and west of Lamoni (KLWD) to Mason City (KMCW). && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && DISCUSSION...Curtis AVIATION...Cogil
Hazardous Weather Outlook National Weather Service Des Moines IA 424 AM CDT Tue May 26 2020 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097-270930- 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- 424 AM CDT Tue May 26 2020 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight A round of non-severe showers and thunderstorms will cross the region this morning. Strong to severe thunderstorms are expected this afternoon with damaging winds, a few quickly forming tornadoes possible and locally heavy rainfall that may lead to localized flooding. .DAYS TWO THROUGH SEVEN...Wednesday through Monday Several more rounds of showers and thunderstorms are forecast through Thursday. Isolated heavy rain is still possible and may again lead to localized flooding. .SPOTTER INFORMATION STATEMENT... Spotters might be needed this afternoon and early evening. REV
The Des Moines radar (KDMX), 19 km away, was scanning. The volume nearest the first event began at 18:20 UTC.
7 tornado, 1 funnel cloud, 1 thunderstorm wind. Local standard time, as filed.
A tornado developed on the north edge of downtown Waukee and moved northwest, causing minor damage at a church and car dealership. The tornado also removed some shingles and roofing to a new house that was still under construction.
Trained spotter reported apparent funnel cloud.
Numerous videos on social media captured the tornado in rural areas between Waukee and Dallas Center. The tornado impacted no damage indicators, therefore the EFU rating.
A storm chaser caught a brief tornado in rural Boone county. The tornado did not impact any damage indicators, hence the EFU rating.
Storm chaser observed a very brief tornado between Boone and Ogden south of Highway 30. The tornado did not impact any damage indicators, hence the EFU rating.
A tornado developed just north of the Wright County/Hamilton County line and moved north. Significant tree damage occurred along the path and a large machine shed was destroyed.
Storm Chaser observed a tornado north of Adair in rural Guthrie county. The tornado had an intermittent path with no damage indicators impacted, therefore the EFU rating.
Storm Chasers captured a brief tornado in western Guthrie county. The tornado was in a rural location with no damage indicators impacted, therefore the EFU rating.
Public report of roof damage to a barn provided via social media.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2020Every state in 2020This day in weather historyThe tornado archive for Iowa, 2020Warnings 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: 887328, 890977, 887330, 887331, 887332, 887333, 887334, 887335, 890978.