Ahead of a cold frontal boundary temperatures throughout Iowa were able to reach into the upper 80s to around 90 along with dew points into the mid 60s.  Along with accompanying vertical temperature profiles, MUCAPE values were able to reach into the 3000+ J/kg neighborhood in many spots with low end supportive effective shear around 30-35 kts initially.  As storms triggered in eastern and southeastern Nebraska, they quickly merged into a series of MCSs and tracked northeast into Iowa.  The strongest storms predominantly were located northwest of the Des Moines metro roughly along a line from Omaha to Mason City. Numerous severe wind gusts in excess of 60 mph were reported along with wind damage and occasional severe hail.

Thunderstorm Wind in GREENE, IOWA
From 16-MAY-17 20:10:00 to 16-MAY-17 20:10:00 (CST-6)
Location: GRAND JCT
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Amateur radio operator reported 6 inch diameter tree limbs down and blocking the road.

Hail in KOSSUTH, IOWA
From 16-MAY-17 20:12:00 to 16-MAY-17 20:12:00 (CST-6)
Location: WESLEY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported quarter sized hail.

Thunderstorm Wind in KOSSUTH, IOWA
From 16-MAY-17 20:25:00 to 16-MAY-17 20:25:00 (CST-6)
Location: WHITTEMORE
Magnitude: 61.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Algona RWIS measured wind gusts to 70 mph.

Thunderstorm Wind in KOSSUTH, IOWA
From 16-MAY-17 20:24:00 to 16-MAY-17 20:24:00 (CST-6)
Location: ALGONA
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported wind gusts around 55 to 60 mph along with pea sized hail.  Several tree limbs down roughly 2 to 3 inches in diameter.

Thunderstorm Wind in WEBSTER, IOWA
From 16-MAY-17 20:25:00 to 16-MAY-17 20:25:00 (CST-6)
Location: BADGER
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported strong winds, including tree branches down, wind broken out, and power out.  No estimate on wind speed at the time.

Thunderstorm Wind in KOSSUTH, IOWA
From 16-MAY-17 20:27:00 to 16-MAY-17 20:27:00 (CST-6)
Location: ALGONA
Magnitude: 61.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported wind gusts to around 70 mph.

Hail in WINNEBAGO, IOWA
From 16-MAY-17 20:31:00 to 16-MAY-17 20:31:00 (CST-6)
Location: LELAND
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported quarter sized hail ongoing at the time of the report.

Thunderstorm Wind in WRIGHT, IOWA
From 16-MAY-17 20:35:00 to 16-MAY-17 20:35:00 (CST-6)
Location: CLARION ARPT
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Clarion AWOS reported 48 mph winds with gusts to 60 mph.

Thunderstorm Wind in KOSSUTH, IOWA
From 16-MAY-17 20:19:00 to 16-MAY-17 20:25:00 (CST-6)
Location: ALGONA
Magnitude: 65.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Numerous downed trees some up to 18 inches in diameter across the county, some buildings damaged and numerous power lines down. A railroad crossing arm was snapped off and a garage was destroyed in Whittemore, some outbuildings and a house were damaged near town as well. Agricultural impacts as well with machinery blown over, bent up and also seed loss.

Thunderstorm Wind in SAC, IOWA
From 16-MAY-17 19:08:00 to 16-MAY-17 19:08:00 (CST-6)
Location: ODEBOLT
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Local fire department reported 60 to 70 mph wind gusts.

Hail in POCAHONTAS, IOWA
From 16-MAY-17 19:25:00 to 16-MAY-17 19:25:00 (CST-6)
Location: FONDA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported quarter sized hail in Fonda.

Thunderstorm Wind in WEBSTER, IOWA
From 16-MAY-17 19:43:00 to 16-MAY-17 19:43:00 (CST-6)
Location: GOWRIE
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Amateur radio operator reported wind gusts to 60 mph. Time estimated by radar.

Hail in WEBSTER, IOWA
From 16-MAY-17 19:43:00 to 16-MAY-17 19:43:00 (CST-6)
Location: FARNHAMVILLE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported quarter sized hail.

Thunderstorm Wind in CALHOUN, IOWA
From 16-MAY-17 19:44:00 to 16-MAY-17 19:44:00 (CST-6)
Location: MANSON
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported wind gusts to 60 mph.

Thunderstorm Wind in BOONE, IOWA
From 16-MAY-17 20:36:00 to 16-MAY-17 20:36:00 (CST-6)
Location: ERICSON
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported gusts to 60 mph along with nickel sized hail and heavy rainfall.

Thunderstorm Wind in CALHOUN, IOWA
From 16-MAY-17 19:45:00 to 16-MAY-17 19:45:00 (CST-6)
Location: JOLLEY
Magnitude: 63.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Rockwell City RWIS recorded 73 mph wind gust.

Thunderstorm Wind in CERRO GORDO, IOWA
From 16-MAY-17 21:05:00 to 16-MAY-17 21:05:00 (CST-6)
Location: MASON CITY
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported wind gusts to around 60 mph in the downtown area.  Power out as well.

Hail in STORY, IOWA
From 16-MAY-17 21:15:00 to 16-MAY-17 21:15:00 (CST-6)
Location: ZEARING
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Coop observer reported quarter sized hail.

Thunderstorm Wind in TAYLOR, IOWA
From 16-MAY-17 21:55:00 to 16-MAY-17 21:55:00 (CST-6)
Location: BEDFORD
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Coop observer reported wind gusts to 65 mph.

Thunderstorm Wind in MARION, IOWA
From 16-MAY-17 23:21:00 to 16-MAY-17 23:21:00 (CST-6)
Location: KNOXVILLE
Magnitude: 61.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported trees downed in Knoxville.  One fell on a car and crushed it.

Thunderstorm Wind in WORTH, IOWA
From 16-MAY-17 21:25:00 to 16-MAY-17 21:25:00 (CST-6)
Location: GRAFTON
Magnitude: 62.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter measured a 71 mph wind gust at their home.

Thunderstorm Wind in WEBSTER, IOWA
From 16-MAY-17 20:10:00 to 16-MAY-17 20:10:00 (CST-6)
Location: ROBERTS
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A 50.2 kt gust was recorded by the Fort Dodge RWIS station.

Thunderstorm Wind in CALHOUN, IOWA
From 16-MAY-17 19:50:00 to 16-MAY-17 19:50:00 (CST-6)
Location: KNIERIM
Magnitude: 60.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported a metal garage destroyed.

Heavy Rain in POCAHONTAS, IOWA
From 16-MAY-17 06:00:00 to 17-MAY-17 06:00:00 (CST-6)
Location: POCAHONTAS MUNI ARPT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Coop observer recorded heavy rainfall of 2.24 inches over the last 24 hours.

Thunderstorm Wind in WEBSTER, IOWA
From 16-MAY-17 20:12:00 to 16-MAY-17 20:12:00 (CST-6)
Location: BADGER
Magnitude: 61.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Widespread tree limbs down and a few trees in town. South of town a windmill was bent over and a residential TV/Radio tower was bent over, and grain bins were bent in as well.

Thunderstorm Wind in CARROLL, IOWA
From 16-MAY-17 19:20:00 to 16-MAY-17 19:20:00 (CST-6)
Location: CARROLL
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Large tree branches down in the yard.

Thunderstorm Wind in WEBSTER, IOWA
From 16-MAY-17 19:50:00 to 16-MAY-17 19:50:00 (CST-6)
Location: CALLENDER
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Amateur radio operator reported wind gusts to 60 mph.

Thunderstorm Wind in WEBSTER, IOWA
From 16-MAY-17 19:53:00 to 16-MAY-17 19:53:00 (CST-6)
Location: ROELYN
Magnitude: 61.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Amateur radio operator reported wind gusts to 70 mph.

Thunderstorm Wind in WEBSTER, IOWA
From 16-MAY-17 20:06:00 to 16-MAY-17 20:06:00 (CST-6)
Location: FT DODGE
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported lots of tree damage.  Sizes unknown at the time.

Hail in CRAWFORD, IOWA
From 16-MAY-17 18:43:00 to 16-MAY-17 18:43:00 (CST-6)
Location: MANILLA
Magnitude: 1.75 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported golf ball sized hail in the city of Manilla.

Thunderstorm Wind in SAC, IOWA
From 16-MAY-17 19:09:00 to 16-MAY-17 19:09:00 (CST-6)
Location: ODEBOLT
Magnitude: 61.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported at least 3 large trees down in their neighbor's yard.  Time estimated by radar and previous reports.

Thunderstorm Wind in CARROLL, IOWA
From 16-MAY-17 19:15:00 to 16-MAY-17 19:15:00 (CST-6)
Location: CARROLL NEU ARPT
Magnitude: 62.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Carroll AWOS reported sustained winds of 48 mph and gusts to 71 mph.

Thunderstorm Wind in CERRO GORDO, IOWA
From 16-MAY-17 21:13:00 to 16-MAY-17 21:13:00 (CST-6)
Location: MASON CITY
Magnitude: 61.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported multiple tree limbs down throughout the town of Mason City.  Some have fallen on power lines or are blocking roads.  A few power poles snapped as well.  Power out in multiple locations.  Time estimated by radar.

Thunderstorm Wind in POCAHONTAS, IOWA
From 16-MAY-17 19:50:00 to 16-MAY-17 19:50:00 (CST-6)
Location: POCAHONTAS
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported strong winds and heavy rainfall.  Many streets in town had tree branches down ranging from small sticks to big, round branches.  A tree was snapped at one of the cemeteries on the east side of town.  Standing water throughout town.

Thunderstorm Wind in WEBSTER, IOWA
From 16-MAY-17 19:50:00 to 16-MAY-17 19:50:00 (CST-6)
Location: MOORLAND
Magnitude: 52.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported strong winds, blowing dust, and a tree had fallen on a car.

Thunderstorm Wind in WEBSTER, IOWA
From 16-MAY-17 20:07:00 to 16-MAY-17 20:07:00 (CST-6)
Location: FT DODGE
Magnitude: 61.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported widespread power outages, upwards of 40 foot tall trees down, and estimated at least 70 mph winds.  This is a delayed report.

Thunderstorm Wind in WEBSTER, IOWA
From 16-MAY-17 19:53:00 to 16-MAY-17 19:53:00 (CST-6)
Location: ROELYN
Magnitude: 56.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Amateur radio operator reported a transformer blown down/over.

Thunderstorm Wind in DALLAS, IOWA
From 16-MAY-17 20:10:00 to 16-MAY-17 20:10:00 (CST-6)
Location: PERRY
Magnitude: 65.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported a 4-plex apartment building had its roof blown off.  Time estimated by radar.

Thunderstorm Wind in WEBSTER, IOWA
From 16-MAY-17 20:15:00 to 16-MAY-17 20:15:00 (CST-6)
Location: BADGER
Magnitude: 58.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported a window blown in at their home.  Estimated 60 to 70 mph winds.

Thunderstorm Wind in KOSSUTH, IOWA
From 16-MAY-17 20:25:00 to 16-MAY-17 20:25:00 (CST-6)
Location: ALGONA
Magnitude: 56.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported several tree limbs of various size down and one large tree about 5 to 6 feet in diameter down.  Numerous power outages as well.  Time estimated by radar.

Thunderstorm Wind in WRIGHT, IOWA
From 16-MAY-17 20:45:00 to 16-MAY-17 20:45:00 (CST-6)
Location: BELMOND
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Department of Highways

Iowa DOT reported debris blocking the roadway in both directions on Highway 69.  Time estimated by radar.

Thunderstorm Wind in HANCOCK, IOWA
From 16-MAY-17 20:50:00 to 16-MAY-17 20:50:00 (CST-6)
Location: GARNER
Magnitude: 61.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported shingles on the road, trees and branches down in Garner.  Time estimated by radar.

Thunderstorm Wind in CALHOUN, IOWA
From 16-MAY-17 19:54:00 to 16-MAY-17 19:54:00 (CST-6)
Location: MANSON
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported tree limbs down in Manson.  Size unknown at the time.

Thunderstorm Wind in WEBSTER, IOWA
From 16-MAY-17 20:07:00 to 16-MAY-17 20:07:00 (CST-6)
Location: FT DODGE
Magnitude: 61.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported pea sized hail.  Numerous large trees are down all across the city. More detailed damage report in similarly time stamped LSR.

Thunderstorm Wind in KOSSUTH, IOWA
From 16-MAY-17 20:21:00 to 16-MAY-17 20:21:00 (CST-6)
Location: ALGONA
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter estimated wind gusts to around 60 mph ongoing at the time.

Thunderstorm Wind in MARION, IOWA
From 16-MAY-17 23:12:00 to 16-MAY-17 23:12:00 (CST-6)
Location: BEWBERN
Magnitude: 56.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported numerous trees downed along with power lines down. A tree fell on a house in town.

Thunderstorm Wind in WEBSTER, IOWA
From 16-MAY-17 20:07:00 to 16-MAY-17 20:07:00 (CST-6)
Location: FT DODGE
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported multiple tree limbs down along with a few transformers throughout town.  Power out in many locations.

Thunderstorm Wind in CRAWFORD, IOWA
From 16-MAY-17 18:45:00 to 16-MAY-17 18:45:00 (CST-6)
Location: BUCK GROVE
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported wind gusts up to 70 mph.

Thunderstorm Wind in WEBSTER, IOWA
From 16-MAY-17 20:20:00 to 16-MAY-17 20:20:00 (CST-6)
Location: (FOD)FT DODGE MUNI A
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported 5 to 6 inch diameter tree limbs down.