A relatively cool, but juicy atmosphere existed across the area with southerly surface winds dominating and southwesterly mid and upper level flow. During the early morning hours of the 9th, scattered thunderstorms aided by the low level jet remained predominantly sub-severe with small hail. Through the morning and early afternoon hours, a surface warm front entered and moved across the state from southwest to northeast, all the while increasing MUCAPE values across the southeast half to two thirds of the state into the 2000-4000+ J/kg range. Additionally, moderate to steep low level lapse rates boosted DCAPE values into the 1000-1300 J/kg range, increasing the potential for strong downdrafts and resulting surface winds. Effective bulk shear was marginal through most of the event, yielding around 30 to 40kts.
Resulting storms generally rolled through the state in waves from southwest to northeast, with at least periods of organization. The primary cluster of storms rolled through during the late afternoon, producing a fairly consistent trail severe thunderstorm winds and thunderstorm wind damage from southwest of Des Moines all the way through the Waterloo area. A second round of at least brief sever storms moved through overnight just southeast of the Des Moines metro, but was short lived unlike the cluster earlier in the day.

Thunderstorm Wind in ADAIR, IOWA
From 09-SEP-19 16:46:00 to 09-SEP-19 16:46:00 (CST-6)
Location: HOWE
Magnitude: 61.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported a broken power pole at the intersection of White Pole Road and Adair Street.

Lightning in BUTLER, IOWA
From 09-SEP-19 17:40:00 to 09-SEP-19 17:40:00 (CST-6)
Location: SHELL ROCK
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported that lightning struck a utility pole. This is a delayed report and time estimated from radar.

Thunderstorm Wind in BLACK HAWK, IOWA
From 09-SEP-19 18:02:00 to 09-SEP-19 18:02:00 (CST-6)
Location: (ALO)WATERLOO MUNI A
Magnitude: 54.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Waterloo Regional Airport ASOS recorded 62 mph wind gusts.

Thunderstorm Wind in BLACK HAWK, IOWA
From 09-SEP-19 19:40:00 to 09-SEP-19 19:40:00 (CST-6)
Location: WASHBURN
Magnitude: 50.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported damage to mobile home skirting as well as 2.5 inch diameter tree limbs down. Time estimated from radar.

Thunderstorm Wind in BLACK HAWK, IOWA
From 09-SEP-19 19:48:00 to 09-SEP-19 19:48:00 (CST-6)
Location: LA PORTE CITY
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported estimated 60 mph wind gusts just northwest of La Porte City on Highway 218 near Eagle Road.

Thunderstorm Wind in MARSHALL, IOWA
From 09-SEP-19 18:43:00 to 09-SEP-19 18:43:00 (CST-6)
Location: MARSHALLTOWN ARPT
Magnitude: 51.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Marshalltown Municipal Airport ASOS recorded a 59 mph wind gust.

Thunderstorm Wind in POLK, IOWA
From 09-SEP-19 18:50:00 to 09-SEP-19 18:50:00 (CST-6)
Location: ASHAWA
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported estimated 60 mph wind gusts.

Thunderstorm Wind in POLK, IOWA
From 10-SEP-19 02:50:00 to 10-SEP-19 02:50:00 (CST-6)
Location: FT DES MOINES
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported trees down in the neighborhood, including winds over 60 mph.

Thunderstorm Wind in GUTHRIE, IOWA
From 09-SEP-19 15:00:00 to 09-SEP-19 15:00:00 (CST-6)
Location: MENLO
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager relayed law enforcement reports of 4 to 6 inch diameter tree limbs down in Menlo. Time estimated from radar.

Thunderstorm Wind in BUTLER, IOWA
From 09-SEP-19 17:32:00 to 09-SEP-19 17:32:00 (CST-6)
Location: CLARKSVILLE
Magnitude: 56.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported a large tree limb down on a home in Clarksville. Time estimated from radar.

Thunderstorm Wind in STORY, IOWA
From 09-SEP-19 16:43:00 to 09-SEP-19 16:43:00 (CST-6)
Location: COLLINS
Magnitude: 53.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Storm chaser reported thunderstorm wind gusts of 61 mph via personal equipment. Report came via social media.

Thunderstorm Wind in POLK, IOWA
From 10-SEP-19 02:55:00 to 10-SEP-19 02:55:00 (CST-6)
Location: AVON
Magnitude: 52.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Des Moines Public Safety reported a tree fell on a power line, causing power flashes in south Des Moines.

Thunderstorm Wind in BLACK HAWK, IOWA
From 09-SEP-19 17:40:00 to 09-SEP-19 17:40:00 (CST-6)
Location: CEDAR FALLS
Magnitude: 52.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A trained spotter reported 3 inch tree limbs down on the campus of UNI.

Thunderstorm Wind in STORY, IOWA
From 09-SEP-19 16:25:00 to 09-SEP-19 16:30:00 (CST-6)
Location: ROLAND
Magnitude: 61.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported a 10 to 12 inch tree branch down on a power line. Also tree debris across a 3 to 4 block swath on the north side of town.

Tornado in DALLAS, IOWA
From 09-SEP-19 15:32:00 to 09-SEP-19 15:35:00 (CST-6)
Location: DALLAS CENTER
Tornado F-scale: EFU
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Other Federal Agency

Small tornado moved through open cropland.  No damage indicators were impacted, therefore the rating was EFU.  Path was found using high resolution satellite imagery.

Thunderstorm Wind in STORY, IOWA
From 09-SEP-19 16:30:00 to 09-SEP-19 16:35:00 (CST-6)
Location: MAXWELL
Magnitude: 61.00 EG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Emergency Manager

The Emergency manager reported a swath of corn blown down between Collins and Maxwell.

Tornado in DALLAS, IOWA
From 09-SEP-19 15:33:00 to 09-SEP-19 15:38:00 (CST-6)
Location: MINBURN
Tornado F-scale: EFU
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Other Federal Agency

Tornado remained in open cropland east and northeast of Minburn.  No damage indicators were impacted, therefore the EFU rating.  The tornado path was discovered using high resolution satellite imagery.

Thunderstorm Wind in BOONE, IOWA
From 09-SEP-19 16:01:00 to 09-SEP-19 16:01:00 (CST-6)
Location: BOONE
Magnitude: 56.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported a large tree down at 10th Street and Division.

Thunderstorm Wind in STORY, IOWA
From 09-SEP-19 16:12:00 to 09-SEP-19 16:12:00 (CST-6)
Location: AMES
Magnitude: 61.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Ames Police reported wall of a building pushed in about 6 feet, damage to the walls and doors, contents inside blown around, as well as trees down in the area. Time estimated from radar.

Thunderstorm Wind in BUTLER, IOWA
From 09-SEP-19 17:15:00 to 09-SEP-19 17:15:00 (CST-6)
Location: PARKERSBURG
Magnitude: 56.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported several large tree limbs down throughout Parkersburg, as well as a couple trees reported to have fallen on homes. Time estimated from radar.

Thunderstorm Wind in GRUNDY, IOWA
From 09-SEP-19 17:25:00 to 09-SEP-19 17:25:00 (CST-6)
Location: CONRAD
Magnitude: 56.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported tree damage around Conrad, as well as a couple power lines down. Time estimated from radar.

Thunderstorm Wind in HARDIN, IOWA
From 09-SEP-19 18:07:00 to 09-SEP-19 18:07:00 (CST-6)
Location: HUBBARD
Magnitude: 56.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported multiple trees down south of Hubbard. One of the trees was 24 inches in diameter. Spotter estimated wind gusts over 60 mph.

Thunderstorm Wind in BLACK HAWK, IOWA
From 09-SEP-19 18:22:00 to 09-SEP-19 18:22:00 (CST-6)
Location: CASEBEER HGTS
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported 60 mph wind gusts.

Thunderstorm Wind in BLACK HAWK, IOWA
From 09-SEP-19 18:18:00 to 09-SEP-19 18:18:00 (CST-6)
Location: CEDAR FALLS ARPT
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public reported wind damage via the mPING app.

Thunderstorm Wind in BUTLER, IOWA
From 09-SEP-19 17:33:00 to 09-SEP-19 17:33:00 (CST-6)
Location: SHELL ROCK
Magnitude: 56.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported several large tree limbs, including a few large ones, down throughout the town of Shell Rock. Some were blocking the street. Time estimated from radar.

Thunderstorm Wind in STORY, IOWA
From 09-SEP-19 16:50:00 to 09-SEP-19 16:50:00 (CST-6)
Location: COLLINS
Magnitude: 61.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter estimated 70 mph winds. Also reported 10 inch diameter tree limb down from an older tree, and multiple 3 to 4 inch tree limbs down on newer trees.

Thunderstorm Wind in DALLAS, IOWA
From 09-SEP-19 15:35:00 to 09-SEP-19 15:35:00 (CST-6)
Location: MINBURN
Magnitude: 61.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Minburn Fire Department reported 12 inch diameter tree snapped. The report was relayed by Dallas County Emergency Management and the time is estimated from radar.

Thunderstorm Wind in POLK, IOWA
From 09-SEP-19 15:50:00 to 09-SEP-19 15:50:00 (CST-6)
Location: CROCKER
Magnitude: 61.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported telephone pole leaned over as well as a no passing sign leaned over. This is a delayed report and time estimated from radar.