An area of low pressure skirted the region north of Iowa, tracking generally southeast through the day. Trailing fronts were draped across western Iowa (stalled turned warm front) and back across western Iowa (cold front).
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.
An area of low pressure skirted the region north of Iowa, tracking generally southeast through the day. Trailing fronts were draped across western Iowa (stalled turned warm front) and back across western Iowa (cold front). Initially in the the hours just after midnight, a line of storms initiated along the stalled/warm front in an area of MUCAPE around 1000 J/kg and effective bulk shear of 30-40 kts. While primarily periods of heavy rain and small hail prevailed, a couple of severe hail reports were received. Later in the day as the low pressure center moved into northern Iowa, another series of hail producing storms sparked off in an area along the warm front close to the center of the low. MUCAPE and effective bulk shear values were similar to morning storms.
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 7, 5:46 AM CST, 3 hours 44 minutes earlier.
Area Forecast Discussion National Weather Service Des Moines IA 646 AM CDT Sun May 7 2017 .SHORT TERM.../Today through Tonight/ Issued at 339 AM CDT Sun May 7 2017 Some sensible weather may actually return to the forecast late in the period. Not much going on currently however with mid/upper level ridge still upstream from the southern Plains into the Dakotas. The long wave pattern has progressed just enough to push the surface ridge into the Upper MS Valley inducing warm advection from the Dakotas into MN. Moisture is lacking however and the only clouds are quite high based into MN and may skirt northeast sections today. The low level warm advection won't be too strong however with surface winds staying less than 180 degrees. Thus have kept highs at or just above persistence with better warming potential west. The warm/theta-e advection should persist and lower into tonight and the MUCAPE axis should eventually progress to and through the MO Valley into Monday morning. This may produce isolated elevated showers and storms after 06z. Various models suggest MUCAPEs 500 j/kg or more with 30+kts of effective shear, so while the potential is certainly not great, there could be a few stronger organized storms with some brief hail potential. Have kept the low end PoPs across the SW two-thirds of the forecast area, which most deterministic and ensembles suggest for placement. There are a few outliers farther NE into ARX's area however, like the HRW ARW or NamNest, but confidence isn't there to push PoPs that far north and east as of yet. .LONG TERM.../Monday through Saturday/ Issued at 339 AM CDT Sun May 7 2017 No major changes to the forecast. Monday a warm front will lift across the forecast area. There will be some elevated instability with this boundary and as a result showers and isolated storms will lift across the area through the day. The Southwest half should see this activity in the morning with the Northeast seeing it in the afternoon. The surface low will move out the area but the frontal boundary will sag South again with another surface low developing and this will keep showers and storms going in Missouri and likely into Southern Iowa as well although models are starting to show a little slower trend with precip not making much advancement into Iowa until Wedensday when the upper low over the southwest U.S. begins to lift into the Plains. This will occur Wednesday into Wednesday night and this timeframe will be the next chance for widespread precip across the state. Thursday the models try to develop a large ridge over the West which then takes the low back to the South aided by a low over the Great Lakes that pivots into the Northeast U.S. This would keep the precip South of the state again however there is a lot of things that have to come together and so confidence is low in this overall solution although it appears at most Southern Iowa could get additional rainfall. Friday into Saturday the aforementioned ridge moves into the Rockies putting the Upper Midwest in a general Northwest flow but the models also want to develop a shortwave/low over Minnesota/Wisconsin and drop it South. The Euro and GFS all suggest that some showers will brush the Northeast part of the forecast area while the Canadian digs the low way South and develops a trough over Illinois and Indiana taking the precip further East. Meanwhile another low is developing over the NW U.S. which will play a part in later forecasts. As for temps there will be quite the divide early in the week on either side of the warm front. Highs across the Northeast will generally be in the 60's while across the Southwest highs will be near 80. Mid to late week once the front is South of the area again, highs statewide will be in the 60's. && .AVIATION.../For the 12Z TAFS through 12Z Monday morning/ Issued at 645 AM CDT Sun May 7 2017 Confidence is high in VFR conditions through the evening hours with nothing more than mid cloudiness northeast near KMCW/KALO and mostly clear skies elsewhere. There is medium to high confidence that VFR conditions will persist through the remainder of the period as well, however VFR ceilings are expected to expand overnight along with the potential for isolated weak elevated convection. There is only a slight potential for non-VFR conditions at any particular site, mainly due to visibility restrictions in showers, and not great enough for a mention or even VCSH at this point. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...Small LONG TERM...FAB AVIATION...Small
Hazardous Weather Outlook National Weather Service Des Moines IA 440 AM CDT Sun May 7 2017 IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075- 081>086-092>097-080945- 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- 440 AM CDT Sun May 7 2017 This Hazardous Weather Outlook is for portions of central Iowa. .DAY ONE...Today and tonight Isolated to scattered non-severe thunderstorms are possible late tonight. .DAYS TWO THROUGH SEVEN...Monday through Saturday Scattered non-severe thunderstorms will be possible at times Monday through Tuesday. .SPOTTER INFORMATION STATEMENT... Spotters will not be needed. FAB
The Des Moines radar (KDMX), 63 km away, was scanning. The volume nearest the first event began at 15:28 UTC.
4 hail, 2 heavy rain, 1 lightning. Local standard time, as filed.
Trained spotter reported heavy rainfall of about 2.00 inches over the last 24 hours. This is a location correction to earlier report.
Off duty 911 center manager reported quarter sized hail covering the ground. The hail lasted for about 5 minutes.
Public reported heavy rainfall of 2.00 inches via social media.
A family reported seeing a red and orange fireball before realizing their neighbor's home was on fire. A tall tree behind the home appeared to have been struck on fire as well.
Trained spotter reported roads covered in up to ping pong ball sized hail in Clear Lake.
Trained spotter reported up to quarter sized hail.
Public reported quarter sized hail via social media.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2017Every state in 2017This day in weather historyWarnings in Iowa, May 2017
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: 687846, 687843, 687844, 695971, 687847, 687849, 687850.