An eventful day played out across Iowa, carried out in two parts. First was a wave of strong to severe storms during the morning hours across much of northern Iowa, followed by a subsequent wave of storms across southern Iowa. Respectively, the storms produced primarily severe hail and then severe winds and heavy rainfall.
Environmentally, the setup was relatively prime for organized convection and to a degree, training storms.  A relatively stationary front (slowly drifting southward later in the day) laid across Iowa from southwest to northeast throughout the day on the 28th. On the warm side of the boundary,  MUCAPE values were in excess of 2000 J/kg already early in the morning, growing to 3000-4000 J/kg by the afternoon. Other supporting factors for organized convection were present as well, including 40 to 50+ kts of effective bulk shear, hail CAPE in excess of 600 J/kg (especially in the morning round), and effective storm relative helicity around or in excess of 200 m2/s2. Understandably, composite indices such as the significant hail parameter and the supercell composite parameter returned values that raised concerns for severe weather potential.
At the end of the day, reports were split into two distinct areas. The first was large hail over northern Iowa with the early morning convection, followed by damaging winds and heavy rainfall with the afternoon and evening convection over southern Iowa.

Heavy Rain in WEBSTER, IOWA
From 28-AUG-18 09:15:00 to 28-AUG-18 17:45:00 (CST-6)
Location: DAYTON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported heavy rainfall of 2.25 inches from the afternoon storms.

Heavy Rain in WAPELLO, IOWA
From 28-AUG-18 10:00:00 to 28-AUG-18 20:30:00 (CST-6)
Location: BLAKESBURG ARPT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported heavy rainfall of 2.71 inches so far today. Report came via social media.

Heavy Rain in WAPELLO, IOWA
From 28-AUG-18 00:00:00 to 29-AUG-18 00:00:00 (CST-6)
Location: (OTM)OTTUMWA INDSTRL
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Ottumwa Regional Airport ASOS recorded heavy rainfall of 4.07 inches over the last 24 hours.

Heavy Rain in DAVIS, IOWA
From 28-AUG-18 04:00:00 to 29-AUG-18 04:00:00 (CST-6)
Location: BLOOMFIELD ARPT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRaHS observer recorded heavy rainfall of 2.04 inches over the last 24 hours.

Heavy Rain in DAVIS, IOWA
From 28-AUG-18 05:00:00 to 29-AUG-18 05:00:00 (CST-6)
Location: PULASKI
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRaHS observer recorded heavy rainfall of 2.08 inches over the last 24 hours.

Heavy Rain in WAPELLO, IOWA
From 28-AUG-18 05:45:00 to 29-AUG-18 05:45:00 (CST-6)
Location: DAHLONEGA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRaHS observer recorded heavy rainfall of 3.50 inches over the last 24 hours.

Heavy Rain in WAPELLO, IOWA
From 28-AUG-18 05:53:00 to 29-AUG-18 05:53:00 (CST-6)
Location: (OTM)OTTUMWA INDSTRL
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Ottumwa Regional Airport ASOS recorded heavy rainfall of 4.19 inches over the last 24 hours.

Thunderstorm Wind in DECATUR, IOWA
From 28-AUG-18 15:58:00 to 28-AUG-18 15:58:00 (CST-6)
Location: GARDEN GROVE
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 100.00K
Reported by: Social Media

Public reported that a large section of mature sweet corn was completely flattened. Time estimated from radar.

Thunderstorm Wind in MAHASKA, IOWA
From 28-AUG-18 16:09:00 to 28-AUG-18 16:09:00 (CST-6)
Location: NEW SHARON
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported a large tree limb covering Market Street and several smaller limbs down around town. Time estimated from radar.

Heavy Rain in DAVIS, IOWA
From 28-AUG-18 06:00:00 to 29-AUG-18 06:00:00 (CST-6)
Location: SAVANNAH
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRaHS observer recorded heavy rainfall of 3.46 inches over the last 24 hours.

Heavy Rain in DAVIS, IOWA
From 28-AUG-18 06:00:00 to 29-AUG-18 06:00:00 (CST-6)
Location: PULASKI
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRaHS observer recorded heavy rainfall of 3.00 inches over the last 24 hours.

Thunderstorm Wind in MAHASKA, IOWA
From 28-AUG-18 16:18:00 to 28-AUG-18 16:18:00 (CST-6)
Location: INDIANAPOLIS
Magnitude: 56.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported 2 to 3 large trees down. Time estimated by radar.

Heavy Rain in DAVIS, IOWA
From 28-AUG-18 06:00:00 to 29-AUG-18 06:00:00 (CST-6)
Location: BLOOMFIELD ARPT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRaHS observer recorded heavy rainfall of 2.50 inches over the last 24 hours.

Heavy Rain in MONROE, IOWA
From 28-AUG-18 06:00:00 to 29-AUG-18 06:00:00 (CST-6)
Location: AVERY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Coop observer recorded heavy rainfall of 2.20 inches over the last 24 hours.

Heavy Rain in WAPELLO, IOWA
From 28-AUG-18 06:00:00 to 29-AUG-18 06:00:00 (CST-6)
Location: ELDON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRaHS observer recorded heavy rainfall of 2.18 inches over the last 24 hours.

Heavy Rain in WAPELLO, IOWA
From 28-AUG-18 06:22:00 to 29-AUG-18 06:22:00 (CST-6)
Location: BLAKESBURG ARPT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRaHS observer recorded heavy rainfall of 3.92 inches over the last 24 hours.

Heavy Rain in WEBSTER, IOWA
From 28-AUG-18 07:00:00 to 29-AUG-18 07:00:00 (CST-6)
Location: FT DODGE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Coop observer recorded heavy rainfall of 2.40 inches over the last 24 hours.

Heavy Rain in WAPELLO, IOWA
From 28-AUG-18 10:00:00 to 29-AUG-18 01:30:00 (CST-6)
Location: AGENCY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported heavy rainfall of 2.10 inches.

Hail in PALO ALTO, IOWA
From 28-AUG-18 05:38:00 to 28-AUG-18 05:38:00 (CST-6)
Location: AYRSHIRE
Magnitude: 3.00 
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported up to around baseball or larger sized hail. Time estimated from radar.

Hail in POCAHONTAS, IOWA
From 28-AUG-18 05:58:00 to 28-AUG-18 05:58:00 (CST-6)
Location: PLOVER
Magnitude: 2.75 
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported baseball sized hail. Time estimated from radar.

Hail in KOSSUTH, IOWA
From 28-AUG-18 06:40:00 to 28-AUG-18 06:40:00 (CST-6)
Location: WESLEY
Magnitude: 1.75 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Public

Public reported quarter to golf ball sized hail.

Hail in KOSSUTH, IOWA
From 28-AUG-18 06:55:00 to 28-AUG-18 06:55:00 (CST-6)
Location: WESLEY
Magnitude: 2.50 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported tennis ball sized hail.

Hail in HANCOCK, IOWA
From 28-AUG-18 06:56:00 to 28-AUG-18 06:56:00 (CST-6)
Location: KANAWHA
Magnitude: 1.75 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Public

Public reported, through local media, golf ball sized hail. Time estimated from radar.

Hail in HANCOCK, IOWA
From 28-AUG-18 07:06:00 to 28-AUG-18 07:06:00 (CST-6)
Location: GARNER
Magnitude: 3.00 
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported, through local media, hail larger than baseball in size. Time estimated from radar.

Hail in HANCOCK, IOWA
From 28-AUG-18 07:10:00 to 28-AUG-18 07:10:00 (CST-6)
Location: GARNER
Magnitude: 2.00 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported hail around ping pong ball in size.

Thunderstorm Wind in CERRO GORDO, IOWA
From 28-AUG-18 07:19:00 to 28-AUG-18 07:19:00 (CST-6)
Location: THORNTON
Magnitude: 56.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported a tree downed onto a house in Thornton. Time and location estimated from radar.

Thunderstorm Wind in CERRO GORDO, IOWA
From 28-AUG-18 07:21:00 to 28-AUG-18 07:21:00 (CST-6)
Location: THORNTON
Magnitude: 56.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported a semi-truck blown over by winds on Interstate 35. One individual was transported to the hospital. Time estimated from radar.

Hail in BOONE, IOWA
From 28-AUG-18 10:33:00 to 28-AUG-18 10:36:00 (CST-6)
Location: LUTHER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported 3 minutes of dime to quarter sized hail.

Hail in POCAHONTAS, IOWA
From 28-AUG-18 12:09:00 to 28-AUG-18 12:09:00 (CST-6)
Location: FONDA
Magnitude: 1.75 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported golf ball sized hail.

Hail in POCAHONTAS, IOWA
From 28-AUG-18 12:20:00 to 28-AUG-18 12:20:00 (CST-6)
Location: FONDA
Magnitude: 1.25 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported half dollar sized hail.

Hail in POCAHONTAS, IOWA
From 28-AUG-18 12:27:00 to 28-AUG-18 12:27:00 (CST-6)
Location: POCAHONTAS
Magnitude: 2.00 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported, relayed by local media, hail around 2 inches in diameter. Time and location estimated from radar and this is a delayed report.

Hail in POCAHONTAS, IOWA
From 28-AUG-18 12:40:00 to 28-AUG-18 12:40:00 (CST-6)
Location: FONDA
Magnitude: 1.75 
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported golf ball sized hail.

Thunderstorm Wind in MARION, IOWA
From 28-AUG-18 15:36:00 to 28-AUG-18 15:36:00 (CST-6)
Location: KNOXVILLE ARPT
Magnitude: 52.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported several tree limbs and power lines down. Time estimated from radar.

Thunderstorm Wind in MARION, IOWA
From 28-AUG-18 15:39:00 to 28-AUG-18 15:39:00 (CST-6)
Location: KNOXVILLE ARPT
Magnitude: 65.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A large egg laying building was destroyed south of Knoxville along Highway 14. The storm moved the south end of the building roughly 40 feet off of its foundation. The walls were anchored into the concrete floor. Time estimated from radar.

Thunderstorm Wind in MARION, IOWA
From 28-AUG-18 15:48:00 to 28-AUG-18 15:48:00 (CST-6)
Location: PELLA
Magnitude: 56.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Large 1 to 2 foot diameter tree branch blown between two homes. Report relayed from KNIA/KRLS radio.

Thunderstorm Wind in MAHASKA, IOWA
From 28-AUG-18 16:22:00 to 28-AUG-18 16:22:00 (CST-6)
Location: OSKALOOSA
Magnitude: 56.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported a large tree down blocking the road near the intersection of N 9th Street and B Ave East. Time estimated from radar.

Thunderstorm Wind in WAPELLO, IOWA
From 28-AUG-18 16:40:00 to 28-AUG-18 16:40:00 (CST-6)
Location: (OTM)OTTUMWA INDSTRL
Magnitude: 61.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Large, tall tree roughly 2 feet in diameter knocked over. This is a delayed report and time estimated from radar.

Thunderstorm Wind in MARION, IOWA
From 28-AUG-18 15:49:00 to 28-AUG-18 15:49:00 (CST-6)
Location: PERSHING
Magnitude: 61.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported several trees and power lines down south of Knoxville. Two trailers were also blown over. Time estimated from radar.

Heavy Rain in LUCAS, IOWA
From 28-AUG-18 08:45:00 to 29-AUG-18 08:45:00 (CST-6)
Location: RUSSELL
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet station recorded heavy rainfall of 2.02 inches over the last 24 hours.

Heavy Rain in DECATUR, IOWA
From 28-AUG-18 09:00:00 to 29-AUG-18 09:00:00 (CST-6)
Location: DAVIS CITY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet station recorded heavy rainfall of 2.06 inches over the last 24 hours.

Heavy Rain in WAPELLO, IOWA
From 28-AUG-18 09:20:00 to 29-AUG-18 09:20:00 (CST-6)
Location: OTTUMWA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet station recorded heavy rainfall of 2.06 inches over the last 24 hours.

Heavy Rain in WAPELLO, IOWA
From 28-AUG-18 09:25:00 to 29-AUG-18 09:25:00 (CST-6)
Location: OTTUMWA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet station recorded heavy rainfall of 2.45 inches over the last 24 hours.

Heavy Rain in WAPELLO, IOWA
From 28-AUG-18 09:29:00 to 29-AUG-18 09:29:00 (CST-6)
Location: RUTLEDGE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Mesonet station recorded heavy rainfall of 3.19 inches over the last 24 hours.

Thunderstorm Wind in MARION, IOWA
From 28-AUG-18 15:48:00 to 28-AUG-18 15:48:00 (CST-6)
Location: PELLA
Magnitude: 61.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Broadcast Media

KNIA/KRLS Radio reported, via social media, several large trees snapped on the Pella Golf and Country Club. Power lines were also reported down throughout Pella.

Heavy Rain in WEBSTER, IOWA
From 28-AUG-18 04:00:00 to 29-AUG-18 04:00:00 (CST-6)
Location: TARA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRaHS observer recorded heavy rainfall of 2.43 inches over the last 24 hours.

Heavy Rain in DAVIS, IOWA
From 28-AUG-18 07:00:00 to 29-AUG-18 07:00:00 (CST-6)
Location: PULASKI
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRaHS observer recorded heavy rainfall of 3.41 inches over the last 24 hours.

Hail in ADAIR, IOWA
From 28-AUG-18 10:10:00 to 28-AUG-18 10:14:00 (CST-6)
Location: ARBOR HILL
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Amateur radio operator reported around 4 minutes of time to penny sized hail.

Hail in FRANKLIN, IOWA
From 28-AUG-18 11:55:00 to 28-AUG-18 11:55:00 (CST-6)
Location: LATIMER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported quarter sized hail on the north side of Latimer at about 1255 pm.

Hail in POCAHONTAS, IOWA
From 28-AUG-18 12:30:00 to 28-AUG-18 12:30:00 (CST-6)
Location: POCAHONTAS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported quarter sized hail.

Thunderstorm Wind in MARION, IOWA
From 28-AUG-18 15:37:00 to 28-AUG-18 15:37:00 (CST-6)
Location: KNOXVILLE
Magnitude: 56.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported several trees and power lines down throughout town. Time estimated from radar.

Thunderstorm Wind in MARION, IOWA
From 28-AUG-18 15:50:00 to 28-AUG-18 15:50:00 (CST-6)
Location: PERSHING
Magnitude: 61.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported that one residence had about 300 square feet of shingles blown off their roof.

Thunderstorm Wind in MARION, IOWA
From 28-AUG-18 15:52:00 to 28-AUG-18 15:52:00 (CST-6)
Location: FLAGLER
Magnitude: 56.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported power lines and several tree limbs down. Time estimated from radar.

Thunderstorm Wind in WAPELLO, IOWA
From 28-AUG-18 17:10:00 to 28-AUG-18 17:10:00 (CST-6)
Location: BLAKESBURG
Magnitude: 61.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported that the small town of Blakesburg had a lot of tree damage, including several trees falling on houses. Extent of damage was unknown at the time. Report came via social media.

Hail in WRIGHT, IOWA
From 28-AUG-18 11:40:00 to 28-AUG-18 11:40:00 (CST-6)
Location: CLARION
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in WAPELLO, IOWA
From 28-AUG-18 17:10:00 to 28-AUG-18 17:10:00 (CST-6)
Location: BLAKESBURG
Magnitude: 56.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported 60 to 70 mph wind gusts. Several large trees and 2 to 6 inch diameter tree limbs were down as a result. Report came in via social media.

Thunderstorm Wind in WAPELLO, IOWA
From 28-AUG-18 17:35:00 to 28-AUG-18 17:35:00 (CST-6)
Location: RUTLEDGE
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Public

Public reported, via the mPING app, 3 inch tree limbs and power poles broken.

Thunderstorm Wind in MARION, IOWA
From 28-AUG-18 16:02:00 to 28-AUG-18 16:02:00 (CST-6)
Location: TRACY
Magnitude: 56.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported that a large tree fell on a residence, causing significant damage to the roof and interior rooms. Time estimated from radar.

Thunderstorm Wind in MONROE, IOWA
From 28-AUG-18 16:20:00 to 28-AUG-18 16:20:00 (CST-6)
Location: ALBIA
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported up to 60 mph wind gusts, with small tree branches down.

Hail in PALO ALTO, IOWA
From 28-AUG-18 06:12:00 to 28-AUG-18 06:12:00 (CST-6)
Location: WEST BEND
Magnitude: 2.75 
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported windows broken on houses and cars by hail. This is a delayed report and time estimated from radar.

Thunderstorm Wind in WAPELLO, IOWA
From 28-AUG-18 16:35:00 to 28-AUG-18 16:35:00 (CST-6)
Location: (OTM)OTTUMWA INDSTRL
Magnitude: 59.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Ottumwa Regional Airport ASOS recorded a 68 mph wind gust.