As an upper-level jet streak moved into southeast South Dakota during the late evening of August 4, a cluster of storms developed in south central South Dakota along and in advance of a surface trough axis where elevated instability was over 2000 J/kg. These storms moved in a general east to southeast direction into northwest Iowa, becoming outflow dominant with damaging winds and even a rare nighttime tornado.

Hail in SIOUX, IOWA
From 05-AUG-18 01:40:00 to 05-AUG-18 01:41:00 (CST-6)
Location: FAIRVIEW
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm Wind in SIOUX, IOWA
From 05-AUG-18 01:44:00 to 05-AUG-18 01:46:00 (CST-6)
Location: ROCK VLY
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Social media report of a large tree down in the city of Rock Rapids. Time estimated from radar.

Thunderstorm Wind in SIOUX, IOWA
From 05-AUG-18 01:45:00 to 05-AUG-18 01:48:00 (CST-6)
Location: HAWARDEN
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Trees and power lines down all across town.

Thunderstorm Wind in SIOUX, IOWA
From 05-AUG-18 01:46:00 to 05-AUG-18 01:48:00 (CST-6)
Location: CARMEL
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Social media reports of a large tree split by high winds. Time estimated from radar.

Thunderstorm Wind in SIOUX, IOWA
From 05-AUG-18 01:56:00 to 05-AUG-18 02:00:00 (CST-6)
Location: SIOUX CENTER
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Scattered trees and power lines down across the entire town.

Thunderstorm Wind in O'BRIEN, IOWA
From 05-AUG-18 02:10:00 to 05-AUG-18 02:12:00 (CST-6)
Location: SHELDON
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Numerous trees and power lines down in Sheldon. Some minor street flooding as well.

Thunderstorm Wind in O'BRIEN, IOWA
From 05-AUG-18 02:18:00 to 05-AUG-18 02:20:00 (CST-6)
Location: ARCHER
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Measured wind gust by the Archer Fire Department.  Heavy rainfall also reported.

Thunderstorm Wind in BUENA VISTA, IOWA
From 05-AUG-18 02:53:00 to 05-AUG-18 02:55:00 (CST-6)
Location: REMBRANDT
Magnitude: 70.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

A five inch diameter tree was snapped in half.

Thunderstorm Wind in CLAY, IOWA
From 05-AUG-18 02:57:00 to 05-AUG-18 02:58:00 (CST-6)
Location: (3SE)SPENCER MUNI AR
Magnitude: 59.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

Tornado in BUENA VISTA, IOWA
From 05-AUG-18 02:45:00 to 05-AUG-18 02:46:00 (CST-6)
Location: LINN GROVE
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Drone video revealed that a short duration QLCS tornado touched down across northwestern Buena Vista county.  The tornado tracked southeast and was on the ground for less than a minute. Damage was limited to crops and some tree branches.

Thunderstorm Wind in CLAY, IOWA
From 05-AUG-18 02:58:00 to 05-AUG-18 03:00:00 (CST-6)
Location: GREENVILLE
Magnitude: 70.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Older barn and hog house destroyed. Heavy damage to newer machine shed. Fallen large limbs caused light damage to farm house.