Between the evening of Wednesday the 6th and sunrise on Thursday the 7th, the majority of the 24-county South Central Nebraska area saw at least some thunderstorm activity. For most places though, storms were fairly weak, producing only rainfall and modest wind gusts. However, there were two glaring and rather localized exceptions featuring ground-truth of severe wind gusts, one in the far northeast portion of the local area and the other in the southwest. More specifically, around 815 p.m. CDT on the 6th, a southward-surging outflow boundary with estimated wind gusts to 70 MPH destroyed a metal outbuilding a few miles northeast of Osceola (northwest of Shelby). Then several hours later, shortly after 3 a.m. CDT on the 7th, a surge of very intense winds along a bowing line segment (measured at 91 MPH on a personal weather station) caused considerable damage in a small portion of western Harlan County between Orleans and Oxford, including: uprooted trees, overturned pivots and windows blown out of a home.
Breaking down the evolution of thunderstorms over the course of this time frame, things first initiated in far northeast portions of the local area during the mid-afternoon and late-evening hours. As early as around 4 p.m. CDT, an isolated storm produced nickel size hail near Fullerton. While this early activity faded quickly, a few hours later a cluster of severe storms developed slightly north of Polk/Nance counties, with the resultant southward-surging outflow causing the Polk County damage before sunset. Interestingly, this damage occurred at least 5-10 miles south of the leading edge of any rainfall. During the next few hours, until around 11 p.m. CDT, a northwest-southeast oriented line of strong storms continued affecting mainly Nance and northern Greeley counties, but there were no additional severe-criteria reports. As the pre-midnight activity was occurring in the northeast, a separate cluster of strong to severe storms developed well off to the west in the Nebraska-Colorado-Kansas border region, eventually tracking into far southwestern portions of the local area between midnight-1 a.m. CDT in the form of a linear mesoscale convective system (MCS). Although the majority of severe-criteria wind gusts associated with this complex focused just to the south within northwest/north central Kansas, a northward-surging bow in the convective line developed rather abruptly over southwestern Harlan County around 2:30 a.m. CDT. This small-scale feature soon caused the aforementioned, extensive-but-localized damage in west-central Harlan County. Winds diminished in intensity as they swept north into Phelps County, but a mesonet station north-northwest of Holdrege still managed a 58 MPH gust at 3:41 a.m. CDT. This was the last severe weather report of the day, as convection steadily weakened and diminished in coverage through the mid-morning hours.
In the mid-upper levels, these events of the 6th-7th occurred in a subtly-forced environment, as Nebraska resided under weak westerly flow along the northern periphery of a ridge extending up from the Southern Plains. As a result, deep-layer wind shear was weak, only averaging around 25 knots or less. However, there was plentiful instability, as the combination of afternoon temperatures in the 90s F and dewpoints well into the 60s F yielded mixed-layer CAPE of 2000-4000 J/kg during the afternoon/early-evening. At the surface, this activity occurred to the south of a west-east oriented, quasi-stationary front draped through northern Nebraska.

Hail in NANCE, NEBRASKA
From 06-JUN-18 15:10:00 to 06-JUN-18 15:10:00 (CST-6)
Location: FULLERTON
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm Wind in POLK, NEBRASKA
From 06-JUN-18 19:15:00 to 06-JUN-18 19:15:00 (CST-6)
Location: SHELBY
Magnitude: 61.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A large metal outbuilding flipped over and a large tree was knocked over as very strong outflow headed south of a line of thunderstorms.

Thunderstorm Wind in HARLAN, NEBRASKA
From 07-JUN-18 02:08:00 to 07-JUN-18 02:08:00 (CST-6)
Location: ORLEANS
Magnitude: 79.00 MG
Property damage: 350.00K
Crop damage: 100.00K
Reported by: Mesonet

The emergency manager reported damage to a farmstead near this mesonet site. Damage included blown down power poles, building damage, uprooted trees, overturned pivots, windows blown out of a home and vehicles.

Thunderstorm Wind in PHELPS, NEBRASKA
From 07-JUN-18 02:41:00 to 07-JUN-18 02:41:00 (CST-6)
Location: HOLDREGE
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in POLK, NEBRASKA
From 06-JUN-18 19:15:00 to 06-JUN-18 19:15:00 (CST-6)
Location: SHELBY
Magnitude: 56.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

NWS cooperative observer reported numerous broken tree branches up to 4 inches in diameter.