To open up the month of May, Iowa saw a pair of thunderstorm rounds move through. First, storms that initiated the afternoon and evening prior in central and eastern Nebraska and progressed into and across Iowa overnight and through the morning of the 1st.  That first line of storms was primarily elevated in nature within an environment of 1000+ J/kg MUCAPE and lackluster effective bulk shear, resulting in mostly sub-severe hail and wind gusts. As the environment cleared out during the morning hours, MUCAPE values approached 2000 J/kg near the cold front across northwest and western Iowa. Effective bulk shear values remained lackluster, under 35 kts in most cases.  Resulting storms that fired up near and ahead of the surface cold front during the mid-afternoon hours generally struggled to sustain rotating updrafts, but were able to drop multiple instances of severe hail, approaching 2 inches in diameter occasionally.

Hail in CASS, IOWA
From 01-MAY-18 02:56:00 to 01-MAY-18 02:56:00 (CST-6)
Location: MARNE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported quarter sized hail via the mPING application.

Hail in DALLAS, IOWA
From 01-MAY-18 15:45:00 to 01-MAY-18 15:45:00 (CST-6)
Location: WOODWARD
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported quarter sized hail.

Hail in BOONE, IOWA
From 01-MAY-18 15:52:00 to 01-MAY-18 15:52:00 (CST-6)
Location: MADRID
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported quarter sized hail.

Hail in MARSHALL, IOWA
From 01-MAY-18 17:24:00 to 01-MAY-18 17:24:00 (CST-6)
Location: ALBION
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported pea to nickle sized hail.

Thunderstorm Wind in DECATUR, IOWA
From 01-MAY-18 09:15:00 to 01-MAY-18 09:15:00 (CST-6)
Location: (30I)LAMONI MUNI ARP
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Lamoni Municipal Airport ASOS station recorded a 60 mph wind gust.

Thunderstorm Wind in UNION, IOWA
From 01-MAY-18 06:00:00 to 01-MAY-18 06:00:00 (CST-6)
Location: CRESTON ARPT
Magnitude: 56.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported two barns damaged west of Creston.

Lightning in POLK, IOWA
From 01-MAY-18 06:00:00 to 01-MAY-18 06:25:00 (CST-6)
Location: CLOVER HILLS
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Social Media

Public shared video of a lightning strike that resulted in setting a tree on fire and rupturing a gas line behind Enterprise Rent-a-Car.

Hail in BOONE, IOWA
From 01-MAY-18 16:06:00 to 01-MAY-18 16:06:00 (CST-6)
Location: MADRID
Magnitude: 1.50 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported up to about ping pong ball sized hail.

Hail in DALLAS, IOWA
From 01-MAY-18 15:49:00 to 01-MAY-18 15:49:00 (CST-6)
Location: WOODWARD
Magnitude: 1.75 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported up to golf ball sized hail mixed in with smaller hail.

Hail in BOONE, IOWA
From 01-MAY-18 16:09:00 to 01-MAY-18 16:09:00 (CST-6)
Location: MADRID
Magnitude: 1.75 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported up to golf ball sized hail.

Hail in STORY, IOWA
From 01-MAY-18 16:29:00 to 01-MAY-18 16:29:00 (CST-6)
Location: ONTARIO
Magnitude: 1.50 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported ping pong ball sized hail.

Hail in POCAHONTAS, IOWA
From 01-MAY-18 16:30:00 to 01-MAY-18 16:30:00 (CST-6)
Location: LAURENS
Magnitude: 1.25 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Public

Public reported half dollar sized hail.  The report was relayed via county Sheriff's Office.

Hail in POCAHONTAS, IOWA
From 01-MAY-18 16:46:00 to 01-MAY-18 16:46:00 (CST-6)
Location: LAURENS
Magnitude: 1.75 
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported golf ball sized hail via social media.

Hail in HUMBOLDT, IOWA
From 01-MAY-18 17:44:00 to 01-MAY-18 17:44:00 (CST-6)
Location: BODE
Magnitude: 1.50 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported small half inch brances broken off and roof damage from up to ping pong ball sized hail this evening.  This is a delayed report.

Hail in HUMBOLDT, IOWA
From 01-MAY-18 17:53:00 to 01-MAY-18 17:53:00 (CST-6)
Location: BODE
Magnitude: 1.25 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported half dollar sized hail.

Hail in GUTHRIE, IOWA
From 01-MAY-18 15:31:00 to 01-MAY-18 15:31:00 (CST-6)
Location: JAMAICA
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

NWS employee reported up to penny size hail lasting about 15 to 30 seconds.

Hail in STORY, IOWA
From 01-MAY-18 16:30:00 to 01-MAY-18 16:30:00 (CST-6)
Location: AMES
Magnitude: 1.50 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported ping pong ball sized hail.

Hail in STORY, IOWA
From 01-MAY-18 16:30:00 to 01-MAY-18 16:30:00 (CST-6)
Location: ONTARIO
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported quarter sized hail.

Hail in STORY, IOWA
From 01-MAY-18 16:22:00 to 01-MAY-18 16:22:00 (CST-6)
Location: AMES
Magnitude: 1.25 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported half dollar sized hail.

Hail in STORY, IOWA
From 01-MAY-18 16:15:00 to 01-MAY-18 16:15:00 (CST-6)
Location: ONTARIO
Magnitude: 1.00 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported nickel sized hail, a few quarters as well.

Hail in POLK, IOWA
From 01-MAY-18 06:25:00 to 01-MAY-18 06:25:00 (CST-6)
Location: WINDSOR HGTS
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported mostly pea size hail, but a few larger stones up to nickel size were observed.

Hail in POCAHONTAS, IOWA
From 01-MAY-18 16:54:00 to 01-MAY-18 16:54:00 (CST-6)
Location: LAURENS
Magnitude: 1.50 
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Public

Public reported large hail up to ping pong ball sized covering the ground.

Hail in GUTHRIE, IOWA
From 01-MAY-18 15:25:00 to 01-MAY-18 15:25:00 (CST-6)
Location: MONTEITH
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported nickel hail with a few quarter size pieces as well as the storm moved through Panora.

Hail in STORY, IOWA
From 01-MAY-18 16:27:00 to 01-MAY-18 16:27:00 (CST-6)
Location: AMES ARPT
Magnitude: 1.00 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported quarter sized hail.

Hail in POLK, IOWA
From 01-MAY-18 07:00:00 to 01-MAY-18 07:00:00 (CST-6)
Location: ALTOONA
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Nickel hail was reported.

Hail in POCAHONTAS, IOWA
From 01-MAY-18 16:55:00 to 01-MAY-18 16:55:00 (CST-6)
Location: ROLFE
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Penny size hail was reported in Rolfe.

Hail in HUMBOLDT, IOWA
From 01-MAY-18 17:55:00 to 01-MAY-18 17:55:00 (CST-6)
Location: LIVERMORE
Magnitude: 2.00 
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Social Media

Large hail was reported with a picture of an estimated 2 inch hail stone.

Hail in STORY, IOWA
From 01-MAY-18 16:46:00 to 01-MAY-18 16:46:00 (CST-6)
Location: NEVADA
Magnitude: 2.00 
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported 2 inch hail.

Hail in HUMBOLDT, IOWA
From 01-MAY-18 17:48:00 to 01-MAY-18 17:48:00 (CST-6)
Location: BODE
Magnitude: 1.50 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported ping pong ball sized hail.

Hail in STORY, IOWA
From 01-MAY-18 16:45:00 to 01-MAY-18 16:45:00 (CST-6)
Location: NEVADA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported quarter sized hail.