After morning heavy rainfall over northern Iowa, conditions cleared out for the late morning and afternoon hours ahead of an impending cold front. As a result, MUCAPE values were able to climb from below 1000 J/kg to over 2000 J/kg by the mid to late afternoon hours, coincident with 30 to 40+ kts of effective bulk shear,  and DCAPE approaching 1000 J/kg ahead of the boundary.  By the afternoon, storms initiated along the impending cold front, quickly taking a linear form with the near-parallel 0-6km shear, and continued to move eastward across the state. While much of the line remained sub-severe, sections of the line were able to produce both severe wind gust and wind damage, west of Interstate 35.  A tornado also occurred in far northwest Emmet county which moved in from Dickinson county but produced only crop damage.

Thunderstorm Wind in EMMET, IOWA
From 20-SEP-18 16:30:00 to 20-SEP-18 16:30:00 (CST-6)
Location: ESTHERVILLE
Magnitude: 56.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported that a large tree was uprooted. This is a delayed report.

Thunderstorm Wind in SAC, IOWA
From 20-SEP-18 16:52:00 to 20-SEP-18 16:52:00 (CST-6)
Location: SCHALLER
Magnitude: 56.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported trees down on power lines along Dean Ave. Time estimated from radar.

Thunderstorm Wind in PALO ALTO, IOWA
From 20-SEP-18 16:52:00 to 20-SEP-18 16:52:00 (CST-6)
Location: EMMETSBURG
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Storm chaser measured 60 mph wind gusts via their personal anemometer.

Thunderstorm Wind in KOSSUTH, IOWA
From 20-SEP-18 17:15:00 to 20-SEP-18 17:15:00 (CST-6)
Location: ALGONA MUNI ARPT
Magnitude: 55.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Algona Municipal Airport AWOS recorded a 63 mph wind gust.

Thunderstorm Wind in KOSSUTH, IOWA
From 20-SEP-18 17:15:00 to 20-SEP-18 17:15:00 (CST-6)
Location: ALGONA
Magnitude: 56.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Public

Public reported trees and power lines down throughout town.

Thunderstorm Wind in CALHOUN, IOWA
From 20-SEP-18 17:30:00 to 20-SEP-18 17:30:00 (CST-6)
Location: ROCKWELL CITY
Magnitude: 53.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Rockwell City Iowa RWIS station recorded 61 mph wind gusts.

Tornado in EMMET, IOWA
From 20-SEP-18 16:26:00 to 20-SEP-18 16:28:00 (CST-6)
Location: ESTHERVILLE
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Tornado moved into Emmet county from Dickinson county north of 150th Street.  The tornado remained in rural agricultural land producing only crop damage.  Tornado dissipated upon moving into a wetland area.

Thunderstorm Wind in CALHOUN, IOWA
From 20-SEP-18 17:40:00 to 20-SEP-18 17:40:00 (CST-6)
Location: ROCKWELL CITY
Magnitude: 56.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported up to 10 inch diameter tree branches down.

Thunderstorm Wind in HANCOCK, IOWA
From 20-SEP-18 17:50:00 to 20-SEP-18 17:50:00 (CST-6)
Location: BRITT
Magnitude: 56.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Law enforcement reported a tree down and blocking a road in the town of Britt.

Thunderstorm Wind in EMMET, IOWA
From 20-SEP-18 16:31:00 to 20-SEP-18 16:31:00 (CST-6)
Location: ESTHERVILLE
Magnitude: 61.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Emergency manager reported a car wash roof completely removed and destroyed. Provided picture via social media. This is a delayed report and time and location estimated.

Thunderstorm Wind in CALHOUN, IOWA
From 20-SEP-18 17:31:00 to 20-SEP-18 17:31:00 (CST-6)
Location: LAVINIA
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public estimated wind gusts to 60 to 70 mph while driving.

Flood in BUTLER, IOWA
From 20-SEP-18 20:49:00 to 21-SEP-18 20:30:00 (CST-6)
Location: DUMONT
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 100.00K
Reported by: Department of Highways

Iowa DOT and local law enforcement reported flooding along Highway 3 in both directions in Dumont. The road was closed overnight and the flooding ended as the level of the Shell Rock River and Hargrave Creek near Dumont both started to fall.

Thunderstorm Wind in EMMET, IOWA
From 20-SEP-18 16:30:00 to 20-SEP-18 16:30:00 (CST-6)
Location: ESTHERVILLE
Magnitude: 61.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported a dugout at a local baseball field was destroyed and that the bowling alley experienced partial roof destruction. This is a delayed report.

Thunderstorm Wind in EMMET, IOWA
From 20-SEP-18 16:32:00 to 20-SEP-18 16:32:00 (CST-6)
Location: ESTHERVILLE ARPT
Magnitude: 65.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Estherville Municipal Airport ASOS recorded a 75 mph wind gust.

Thunderstorm Wind in PALO ALTO, IOWA
From 20-SEP-18 16:50:00 to 20-SEP-18 16:50:00 (CST-6)
Location: EMMETSBURG
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported power line down in town.

Thunderstorm Wind in EMMET, IOWA
From 20-SEP-18 16:30:00 to 20-SEP-18 16:30:00 (CST-6)
Location: ESTHERVILLE
Magnitude: 56.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Social Media

Public reported a tree uprooted. This is a delayed report.