General surface high pressure remained in the region, keeping the area hot. With moisture off the from remnants of Alberto and general southerly flow down to the Gulf of Mexico, moisture was fairly plentiful with surface dew points in the mid to upper 60s. Support for sustained severe weather was fairly lackluster, with limited hail CAPE, negligible effective shear, but overall SBCAPE values did exceed 3000 to 4000 J/kg. DCAPE values were relatively high in excess of 1000 to 1200 J/kg, raising concern for strong downdrafts/microbursts.
Lingering convection from western Kansas the day before slowly worked towards western Iowa in the morning hours as waves ejected from a western upper level trough. Additionally, weak warm air advection aided initial storm initiation across the western half of Iowa ahead of the larger wave moving off the Rockies. Initially, numerous storms were seen by early afternoon with most being sub-severe. Outflows form early storms also proceeded to initiate subsequent storms, eventually congealing briefly into a linear looking structure. Nearly all severe reports received were wind related from microbursts and collapsing storms as well as one landspout near Ames. Power outages occurred with the storms with at over 9,000 customers without power at one time or another between Ames and Des Moines.

Hail in STORY, IOWA
From 29-MAY-18 14:38:00 to 29-MAY-18 14:38:00 (CST-6)
Location: NEVADA
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported nickel sized hail.

Thunderstorm Wind in STORY, IOWA
From 29-MAY-18 14:48:00 to 29-MAY-18 14:48:00 (CST-6)
Location: NEVADA
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Public relayed picture of tree limbs at least 3 inches in diameter down.

Hail in CRAWFORD, IOWA
From 29-MAY-18 14:50:00 to 29-MAY-18 14:50:00 (CST-6)
Location: DOW CITY
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported nickel sized hail.

Thunderstorm Wind in STORY, IOWA
From 29-MAY-18 15:10:00 to 29-MAY-18 15:10:00 (CST-6)
Location: AMES
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported 4 inch tree limb down, though tree was rotten in the center. Several displaced garbage cans as well.

Thunderstorm Wind in HUMBOLDT, IOWA
From 29-MAY-18 15:55:00 to 29-MAY-18 15:55:00 (CST-6)
Location: THOR
Magnitude: 61.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported several large tree limbs and even a few trees snapped at the base throughout the town of Thor. One tree was roughly 18 inches in diameter and about 50 feet tall and snapped at the base. Some houses had trees that fell on their roof, unknown extent of damage at the time. Time was estimated from radar.

Thunderstorm Wind in WAYNE, IOWA
From 29-MAY-18 16:14:00 to 29-MAY-18 16:14:00 (CST-6)
Location: HUMESTON
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported multiple tree limbs down in excess of 3 inches in diameter. This is a delayed report.

Thunderstorm Wind in WEBSTER, IOWA
From 29-MAY-18 16:30:00 to 29-MAY-18 16:30:00 (CST-6)
Location: CALLENDER
Magnitude: 61.00 EG
Property damage: 70.00K
Crop damage: 0.00K
Reported by: Public

Public reported a modern farm building destroyed with walls and roof collapsed. Time was estimated from radar.

Thunderstorm Wind in KOSSUTH, IOWA
From 29-MAY-18 16:35:00 to 29-MAY-18 16:35:00 (CST-6)
Location: ALGONA MUNI ARPT
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Algona Airport AWOS station recorded a 58 mph wind gust.

Thunderstorm Wind in POLK, IOWA
From 29-MAY-18 16:36:00 to 29-MAY-18 16:36:00 (CST-6)
Location: FT DES MOINES
Magnitude: 56.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Media reported a tree uprooted and fell onto a house at Burnham Ave in Des Moines.

Thunderstorm Wind in POLK, IOWA
From 29-MAY-18 16:40:00 to 29-MAY-18 16:40:00 (CST-6)
Location: FT DES MOINES
Magnitude: 56.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Multiple trees down along Fleur Drive in Des Moines.

Thunderstorm Wind in POLK, IOWA
From 29-MAY-18 16:36:00 to 29-MAY-18 16:36:00 (CST-6)
Location: FT DES MOINES
Magnitude: 56.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported several large tree limbs down around 7 to 8 inches in diameter along with playground equipment blown over.

Thunderstorm Wind in POLK, IOWA
From 29-MAY-18 16:37:00 to 29-MAY-18 16:37:00 (CST-6)
Location: DES MOINES
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported 4 to 6 inch tree branches down.

Lightning in CASS, IOWA
From 29-MAY-18 16:55:00 to 29-MAY-18 16:55:00 (CST-6)
Location: ATLANTIC
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Broadcast Media

KJAN Radio reported lightning struck outdoor wiring and entered a house, causing smoldering insulation in the attic.  Time was estimated from radar.

Thunderstorm Wind in DALLAS, IOWA
From 29-MAY-18 17:24:00 to 29-MAY-18 17:24:00 (CST-6)
Location: REDFIELD
Magnitude: 56.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Public

Public reported a 2 foot diameter tree fell on I Ave.

Thunderstorm Wind in PALO ALTO, IOWA
From 29-MAY-18 17:25:00 to 29-MAY-18 17:25:00 (CST-6)
Location: DEPEW
Magnitude: 56.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported several large tree branches down and a severely damaged outbuilding or garage on a farmstead northeast of Emmetsburg.

Thunderstorm Wind in DALLAS, IOWA
From 29-MAY-18 17:30:00 to 29-MAY-18 17:30:00 (CST-6)
Location: HADDEN HILL
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported 65 mph wind gusts.

Thunderstorm Wind in BOONE, IOWA
From 29-MAY-18 17:45:00 to 29-MAY-18 17:45:00 (CST-6)
Location: BOONE
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported a few large tree branches down in Boone.  Sizes ranged from about 3 to 6 inches in diameter.

Thunderstorm Wind in STORY, IOWA
From 29-MAY-18 17:50:00 to 29-MAY-18 17:50:00 (CST-6)
Location: AMES
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Unknown

Iowa DOT RWIS station recorded a 58 mph wind gust.

Thunderstorm Wind in POLK, IOWA
From 29-MAY-18 16:50:00 to 29-MAY-18 16:50:00 (CST-6)
Location: DES MOINES
Magnitude: 61.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Broadcast Media

WHO noted damage at Principal Park in the form of right field pole snapped, a picnic table blown 20 feet into the stands, and some damage to the right field wall.

Tornado in STORY, IOWA
From 29-MAY-18 14:58:00 to 29-MAY-18 15:01:00 (CST-6)
Location: AMES
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.10K
Reported by: Public

Video of the landspout was obtained via social media.  A well-formed landspout occurred in open agricultural fields just east of Interstate 35 near Ames.  The landspout remained in ag fields with the only damage to emerging crops as it drifted just west of due north under developing thunderstorms.

Thunderstorm Wind in POLK, IOWA
From 29-MAY-18 16:42:00 to 29-MAY-18 16:42:00 (CST-6)
Location: (DSM)DES MOINES INTL
Magnitude: 56.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported roof damage, siding damage and trees uprooted between SW 28th Pl and Thornton Ave. Lawn furniture and hanging baskets blown away as well.