It was a warm, fairly humid day across the southeast half to two thirds of Iowa with highs in the mid 80s and dew points in the upper 60s. A surface boundary was situated to the north and west of the state, along with lingering outflows within the state from previous convection. SBCAPE values generally peaked in the 2000-3000 J/kg range by the afternoon, devoid of supportive shear though. Storms initiated through parts of central Iowa on northeast along a remnant boundary. The severe nature of the storms were relatively short-lived and relegated to the first few hours of the event.  A single severe wind gust was recorded, but a number of sub-severe to large severe hail reports were received, including a report of 2 inch hail near Huxley, IA.

Hail in STORY, IOWA
From 25-MAY-18 17:44:00 to 25-MAY-18 17:44:00 (CST-6)
Location: SHIPLEY
Magnitude: 1.75 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Public

Public reported estimated golf ball sized hail along I-35 south of Ames. Report came via text message picture.

Hail in STORY, IOWA
From 25-MAY-18 17:53:00 to 25-MAY-18 17:53:00 (CST-6)
Location: CAMBRIDGE
Magnitude: 1.50 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported ping pong ball sized hail at the time of the report and ongoing.

Hail in STORY, IOWA
From 25-MAY-18 17:57:00 to 25-MAY-18 17:57:00 (CST-6)
Location: HUXLEY
Magnitude: 1.75 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Law enforcement relayed spotter reports of up to golf ball sized hail in Huxley.

Hail in MARSHALL, IOWA
From 25-MAY-18 18:43:00 to 25-MAY-18 18:45:00 (CST-6)
Location: MARSHALLTOWN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported quarter sized hail in Marshalltown, still ongoing at the time of the call.

Hail in STORY, IOWA
From 25-MAY-18 17:18:00 to 25-MAY-18 17:18:00 (CST-6)
Location: AMES
Magnitude: 1.50 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Public

Public relayed a picture of half dollar to ping pong ball sized hail on the north side of Ames. The image came via a text message picture.

Hail in STORY, IOWA
From 25-MAY-18 17:07:00 to 25-MAY-18 17:07:00 (CST-6)
Location: ONTARIO
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported nickel sized hail along Cameron School Road in NW Ames.  Report came via amateur radio.

Hail in STORY, IOWA
From 25-MAY-18 17:55:00 to 25-MAY-18 17:55:00 (CST-6)
Location: HUXLEY
Magnitude: 2.00 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported large hail in Huxley via social media.

Thunderstorm Wind in STORY, IOWA
From 25-MAY-18 17:31:00 to 25-MAY-18 17:31:00 (CST-6)
Location: AMES ARPT
Magnitude: 53.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Ames Municipal Airport recorded a 61 mph wind gust.

Hail in STORY, IOWA
From 25-MAY-18 17:12:00 to 25-MAY-18 17:12:00 (CST-6)
Location: AMES
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Amateur radio operator reported quarter sized hail.

Hail in STORY, IOWA
From 25-MAY-18 17:15:00 to 25-MAY-18 17:15:00 (CST-6)
Location: AMES
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported quarter sized hail.

Hail in GRUNDY, IOWA
From 25-MAY-18 17:52:00 to 25-MAY-18 17:52:00 (CST-6)
Location: IVESTER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported quarter sized hail via the mPING app.

Hail in HARDIN, IOWA
From 25-MAY-18 17:52:00 to 25-MAY-18 17:52:00 (CST-6)
Location: UNION
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported quarter sized hail via social media. Time estimated from radar.

Hail in MARSHALL, IOWA
From 25-MAY-18 18:38:00 to 25-MAY-18 18:38:00 (CST-6)
Location: MARSHALLTOWN ARPT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported quarter sized hail. Time was estimated from radar.

Hail in WORTH, IOWA
From 25-MAY-18 19:30:00 to 25-MAY-18 19:30:00 (CST-6)
Location: MANLY
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported estimated nickel sized hail. Time was estimated from radar.

Hail in JASPER, IOWA
From 25-MAY-18 19:49:00 to 25-MAY-18 19:49:00 (CST-6)
Location: MONROE
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported up to nickel sized hail. Report came via text message picture.

Hail in MARION, IOWA
From 25-MAY-18 20:05:00 to 25-MAY-18 20:05:00 (CST-6)
Location: FIFIELD
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported dime to nickel sized hail.

Hail in STORY, IOWA
From 25-MAY-18 17:27:00 to 25-MAY-18 17:27:00 (CST-6)
Location: ONTARIO
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported nickel sized hail.

Hail in STORY, IOWA
From 25-MAY-18 17:56:00 to 25-MAY-18 17:56:00 (CST-6)
Location: HUXLEY
Magnitude: 2.25 
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Large hail nearly tennis ball size was measured and reported in Huxley.

Thunderstorm Wind in STORY, IOWA
From 25-MAY-18 17:34:00 to 25-MAY-18 17:34:00 (CST-6)
Location: AMES ARPT
Magnitude: 53.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A large tree was split and a power pole was blown down.