The state found itself under broad upper level ridging to zonal flow, allowing for a weak cold front to slide into the state and stall around the Interstate 80 corridor during the evening and overnight hours. The environment was fairly ripe for thunderstorm activity, including 2000-3000+ J/kg SBCAPE and hail CAPE values around 500 J/kg, but lacked supportive effective bulk shear with values generally around 30 kts or less.  With the front stalling across central Iowa, and the thermodynamic environment what it was, thunderstorms predominantly lingered across central Iowa through the evening and overnight hours, producing periods of severe hail during the first couple of hours and transitioning to sub-severe storms and a predominant heavy rainfall threat. In the end, there were a number of reports of quarter to near golf ball sized hail, followed by heavy rainfall amounts of 2 to 3+ inches by the morning of the 17th.

Hail in AUDUBON, IOWA
From 16-MAY-19 19:12:00 to 16-MAY-19 19:12:00 (CST-6)
Location: VIOLA CENTER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported up to quarter sized hail along Pheasant Ave.

Hail in DALLAS, IOWA
From 16-MAY-19 19:23:00 to 16-MAY-19 19:23:00 (CST-6)
Location: PANTHER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter driving along Highway 44 reported large hail to quarters or just larger and strong winds kicking up dust in fields.

Hail in MARSHALL, IOWA
From 16-MAY-19 19:03:00 to 16-MAY-19 19:03:00 (CST-6)
Location: MELBOURNE
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 10.00K
Reported by: Public

Public reported quarter sized hail, via social media.

Thunderstorm Wind in MARSHALL, IOWA
From 16-MAY-19 18:53:00 to 16-MAY-19 18:53:00 (CST-6)
Location: LURAY
Magnitude: 54.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

IDOT mesonet station reported 62 mph wind gust.

Hail in MARSHALL, IOWA
From 16-MAY-19 18:54:00 to 16-MAY-19 18:54:00 (CST-6)
Location: MARSHALLTOWN
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported ongoing hail from nickels to ping pong ball in size.

Hail in AUDUBON, IOWA
From 16-MAY-19 19:08:00 to 16-MAY-19 19:08:00 (CST-6)
Location: ROSS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Trained spotter reported nickel to quarter sized hail.

Hail in JASPER, IOWA
From 16-MAY-19 19:49:00 to 16-MAY-19 19:49:00 (CST-6)
Location: NEWTON
Magnitude: 1.25 
Property damage: 20.00K
Crop damage: 20.00K
Reported by: Trained Spotter

Trained spotter reported half dollar sized hail, via social media.

Hail in AUDUBON, IOWA
From 16-MAY-19 18:59:00 to 16-MAY-19 18:59:00 (CST-6)
Location: ROSS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported nickel to quarter sized hail.

Heavy Rain in DALLAS, IOWA
From 16-MAY-19 06:00:00 to 17-MAY-19 08:00:00 (CST-6)
Location: HADDEN HILL
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported heavy rainfall of 2.38 inches from 7am Thursday through 9am Friday.

Heavy Rain in POLK, IOWA
From 16-MAY-19 08:44:00 to 17-MAY-19 08:44:00 (CST-6)
Location: URBANDALE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported heavy rainfall of 2.75 inches over the last 24 hours.

Heavy Rain in DALLAS, IOWA
From 16-MAY-19 18:15:00 to 17-MAY-19 09:00:00 (CST-6)
Location: HADDEN HILL
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

WHO TV reported heavy rainfall of 2.95 inches. Beginning time estimated from radar.

Hail in POLK, IOWA
From 16-MAY-19 18:30:00 to 16-MAY-19 18:30:00 (CST-6)
Location: URBANDALE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported nickel to quarter sized hail.

Hail in POLK, IOWA
From 16-MAY-19 18:31:00 to 16-MAY-19 18:31:00 (CST-6)
Location: WINDSOR HGTS
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported penny sized hail at 48th and Forest Ave in Des Moines.

Hail in POLK, IOWA
From 16-MAY-19 19:50:00 to 16-MAY-19 19:50:00 (CST-6)
Location: LOVINGTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported quarter sized hail, via picture on social media.

Heavy Rain in JASPER, IOWA
From 16-MAY-19 19:30:00 to 17-MAY-19 04:40:00 (CST-6)
Location: NEWTON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported heavy rainfall of 2.25 inches since 10:30 pm Thursday night.

Heavy Rain in MAHASKA, IOWA
From 16-MAY-19 06:00:00 to 17-MAY-19 06:00:00 (CST-6)
Location: LACEY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRaHS observer recorded heavy rainfall of 2.03 inches over the last 24 hours.

Hail in POLK, IOWA
From 16-MAY-19 19:51:00 to 16-MAY-19 19:51:00 (CST-6)
Location: LOVINGTON
Magnitude: 1.25 
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported hail larger than quarters and water covering the roads up to and over the curbs.

Hail in POLK, IOWA
From 16-MAY-19 19:55:00 to 16-MAY-19 20:00:00 (CST-6)
Location: LOVINGTON
Magnitude: 1.50 
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Broadcast Media

The local media reported hail caused damage to the roofs of Hoover High School and Meredith Middle School, making some spaces unusable. Some classes had to be moved, and some ofthe classes were dismissed early on Friday for repairs to be made. Some of the classrooms were flooded as well.

Hail in POLK, IOWA
From 16-MAY-19 20:00:00 to 16-MAY-19 20:00:00 (CST-6)
Location: LOVINGTON
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported half dollar sized hail, via pictures on social media.

Thunderstorm Wind in POLK, IOWA
From 16-MAY-19 20:08:00 to 16-MAY-19 20:08:00 (CST-6)
Location: DES MOINES
Magnitude: 50.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Tree damage reported near 42nd and Forest Ave in Des Moines.

Thunderstorm Wind in DALLAS, IOWA
From 16-MAY-19 20:38:00 to 16-MAY-19 20:38:00 (CST-6)
Location: DEXTER
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Public

Public reported tree limbs greater than 6 inches in diameter broken off. Report via social media with picture. Time altered via radar.

Heavy Rain in POLK, IOWA
From 16-MAY-19 17:00:00 to 17-MAY-19 09:56:00 (CST-6)
Location: ALTOONA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Amateur radio operator reported heavy rainfall of 3.07 inches since 6 pm Thursday.

Hail in POLK, IOWA
From 16-MAY-19 18:32:00 to 16-MAY-19 18:32:00 (CST-6)
Location: URBANDALE
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

NWS Employee reported up to nickel sized hail.

Hail in POLK, IOWA
From 16-MAY-19 18:32:00 to 16-MAY-19 18:32:00 (CST-6)
Location: URBANDALE
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported penny sized hail at Urbandale High School.

Lightning in POLK, IOWA
From 16-MAY-19 20:25:00 to 16-MAY-19 20:25:00 (CST-6)
Location: ASHAWA
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Lightning struck a power pole and knocked out power to the area.

Hail in MARSHALL, IOWA
From 16-MAY-19 18:38:00 to 16-MAY-19 18:38:00 (CST-6)
Location: STATE CENTER
Magnitude: 1.50 
Property damage: 10.00K
Crop damage: 25.00K
Reported by: Emergency Manager

Emergency manager reported ping pong ball sized hail.

Hail in POLK, IOWA
From 16-MAY-19 18:35:00 to 16-MAY-19 18:35:00 (CST-6)
Location: LOVINGTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported quarter sized hail via social media.

Heavy Rain in MAHASKA, IOWA
From 16-MAY-19 06:00:00 to 17-MAY-19 06:00:00 (CST-6)
Location: LACEY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

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

Heavy Rain in POLK, IOWA
From 16-MAY-19 06:00:00 to 17-MAY-19 06:00:00 (CST-6)
Location: LOVINGTON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRaHS observer recorded heavy rainfall of 2.26 inches over the last 24 hours.

Heavy Rain in POLK, IOWA
From 16-MAY-19 06:00:00 to 17-MAY-19 06:00:00 (CST-6)
Location: SAYDELL
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

CoCoRaHS observer recorded heavy rainfall of 2.00 inches over the last 24 hours.

Hail in POLK, IOWA
From 16-MAY-19 20:15:00 to 16-MAY-19 20:15:00 (CST-6)
Location: DES MOINES
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported quarter sized hail, via picture on social media.

Hail in POLK, IOWA
From 16-MAY-19 18:37:00 to 16-MAY-19 18:37:00 (CST-6)
Location: LOVINGTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported nickel to quarter sized hail along with strong winds. No damage seen from winds at the time.

Hail in MARSHALL, IOWA
From 16-MAY-19 18:44:00 to 16-MAY-19 18:44:00 (CST-6)
Location: MARSHALLTOWN
Magnitude: 1.50 
Property damage: 100.00K
Crop damage: 50.00K
Reported by: Trained Spotter

Trained spotter reported ping pong ball sized hail ongoing.

Hail in TAMA, IOWA
From 16-MAY-19 18:59:00 to 16-MAY-19 18:59:00 (CST-6)
Location: TOLEDO
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported golf ball hail at Highway 63 and 275th St.

Hail in AUDUBON, IOWA
From 16-MAY-19 19:00:00 to 16-MAY-19 19:00:00 (CST-6)
Location: GRAY
Magnitude: 1.25 
Property damage: 5.00K
Crop damage: 50.00K
Reported by: Public

Public reported nickel to half dollar sized hail.

Hail in MARSHALL, IOWA
From 16-MAY-19 18:46:00 to 16-MAY-19 18:46:00 (CST-6)
Location: MARSHALLTOWN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported pea, nickel and a few quarter sized hail stones.

Hail in TAMA, IOWA
From 16-MAY-19 18:53:00 to 16-MAY-19 18:53:00 (CST-6)
Location: GLADSTONE
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Tama County Emergency Manager's office relayed report of ongoing heavy rain and nickel sized hail.

Heavy Rain in WARREN, IOWA
From 16-MAY-19 20:00:00 to 17-MAY-19 06:00:00 (CST-6)
Location: INDIANOLA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported heavy rainfall between 11pm Thursday and 7am Friday.

Heavy Rain in WARREN, IOWA
From 16-MAY-19 07:00:00 to 17-MAY-19 07:00:00 (CST-6)
Location: INDIANOLA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Coop observer reported heavy rainfall of 3.22 inches over the last 24 hours.

Heavy Rain in DALLAS, IOWA
From 16-MAY-19 18:00:00 to 17-MAY-19 07:30:00 (CST-6)
Location: SHULER MINE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported heavy rainfall of 3.10 inches during the event. Beginning time estimated from radar.

Hail in TAMA, IOWA
From 16-MAY-19 19:06:00 to 16-MAY-19 19:06:00 (CST-6)
Location: GARWIN
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported penny sized hail.