A powerful upper level low pressure system moved quickly across the central Plains during the day on November 11th. As low pressure moved from Kansas into eastern Nebraska during the day, warm and moist air was pushed northward into the region. This unseasonably warm and moist air led to increasing instability during the afternoon over western Iowa and southeast Nebraska. This combined with the strong wind field associated with the low produced an atmosphere ripe for severe weather. Thunderstorms developed along the cold front in eastern Nebraska by early afternoon, and then increased in coverage and intensity as they tracked east into western Iowa during the early afternoon. Large hail and isolated tornadoes were produced by these thunderstorms.

Thunderstorm Wind in MONTGOMERY, IOWA
From 11-NOV-15 13:44:00 to 11-NOV-15 13:44:00 (CST-6)
Location: RED OAK
Magnitude: 55.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

The wind gust was measured at the local Red Oak airport. The emergency manager reported power poles downed from this storm.

Thunderstorm Wind in SHELBY, IOWA
From 11-NOV-15 14:06:00 to 11-NOV-15 14:06:00 (CST-6)
Location: CORLEY
Magnitude: 66.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: AWOS

Tornado in POTTAWATTAMIE, IOWA
From 11-NOV-15 13:48:00 to 11-NOV-15 13:52:00 (CST-6)
Location: AVOCA
Tornado F-scale: EF1
Property damage: 250.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

The tornado started just south of the County Road 18 to the west of the city of Avoca, Iowa. The tornado tracked to the north northeast through open fields initially. Due to the recent harvest the tornado was easily tracked through the fields due to ground scouring of the left-over corn stocks. The tornado narrowly missed a farmstead along 420th street but did destroy one empty grain bin located across the street from the farm. The tornado continued to track across open fields until it crossed the busy Interstate 80 where a semi was lofted and tossed into a ditch on the north side of the interstate. At this location there were also large hardwood trees that were uprooted. The tornado continued to the northeast into Shelby County.

Tornado in SHELBY, IOWA
From 11-NOV-15 13:52:00 to 11-NOV-15 14:02:00 (CST-6)
Location: SHELBY
Tornado F-scale: EF1
Property damage: 1.20M
Crop damage: 0.00K
Reported by: NWS Storm Survey

This tornado entered Shelby County from Pottawattamie County from the southwest. The tornado impacted a total of 6 farmsteads in the county as it tracked to the north northeast. Damage at these farmsteads was confined to mainly outbuilding being damaged or destroyed, trees uprooted, and electrical power poles downed. The tornado tracked across the western side of the Harlan Airport without doing damage to the airport, but a wind gust associated with the rear-flank downdraft of the storm was measured at 76 mph at the automatic observing equipment on the east side of the airport. The tornado finally ended just to the southeast of the city of Harlan.

Tornado in PAGE, IOWA
From 11-NOV-15 12:48:00 to 11-NOV-15 12:50:00 (CST-6)
Location: NORWICH
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

A couple of storm chasers captured on video a small brief tornado just to the west of Yorktown and north of Highway 2. The tornado appeared to be in open county with no damage reported.

Thunderstorm Wind in SHELBY, IOWA
From 11-NOV-15 14:14:00 to 11-NOV-15 14:14:00 (CST-6)
Location: IRWIN
Magnitude: 62.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet