Severe thunderstorms occurred between Red Cloud and Hebron late in the afternoon on this Thursday. Throughout the morning and early afternoon, a narrow band of light rain, oriented from southwest-northeast, moved from the Nebraska panhandle eastward. By mid-afternoon, this rain band moved into south central Nebraska. About 60 miles ahead of this rain band, scattered thunderstorms began forming, where skies were sunny, from Red Cloud to York. These storms were part of a much larger line that extended from Souix Falls, South Dakota to Hill City, Kansas. Thunderstorms continued to increase in coverage, filling-in between Red Cloud and York. Between 4 and 6 PM CST, some storms became severe. While the majority of storms were still predominantly individual cells, hail occurred in a couple spots over Clay and Webster counties. The largest hail reported was the size of ping pong balls and golf balls in the town of Cowles. Between 5 and 6 PM CST, a squall line formed from Highway 136 in Webster county down into north central Kansas. The northern portion of this line became a small-scale bow echo and moved northeast across Nuckolls, Thayer, and Fillmore counties. Damaging downburst winds snapped off large tree limbs in Red Cloud,  Hebron, and Bruning. Winds were measured at 64 MPH in Nelson and 65 MPH in Davenport.
In the preceding days, an east-west oriented front had become quasi-stationary from the Ohio Valley across central Nebraska to Nevada. During the morning hours on this date, a low formed on the front between North Platte and McCook. This low then accelerated to near Sioux City, Iowa by mid-afternoon with its trailing cold front becoming mobile and moving southeast. The storms formed along this front. In the upper-levels, a subtropical high was over the Tennessee Valley and gradually moved into the Carolinas as a fairly strong shortwave trough moved out of the Northern Rockies into Northern and Central Plains. Immediately ahead of the front, temperatures were in the lower to middle 90s with dewpoints in the lower to middle 60s. Combined with mid-level lapse rates between 7.0 and 7.5 C/km, SBCAPE was between 1500 and 2000 J/kg. Deep layer shear was near 40 kt.

Hail in CLAY, NEBRASKA
From 20-SEP-18 16:15:00 to 20-SEP-18 16:15:00 (CST-6)
Location: CLAY CENTER
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Hail in WEBSTER, NEBRASKA
From 20-SEP-18 16:58:00 to 20-SEP-18 17:09:00 (CST-6)
Location: RED CLOUD
Magnitude: 1.75 
Property damage: 25.00K
Crop damage: 500.00K
Reported by: Trained Spotter

Thunderstorm Wind in NUCKOLLS, NEBRASKA
From 20-SEP-18 17:24:00 to 20-SEP-18 17:24:00 (CST-6)
Location: ABDAL
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in NUCKOLLS, NEBRASKA
From 20-SEP-18 17:32:00 to 20-SEP-18 17:32:00 (CST-6)
Location: NELSON
Magnitude: 56.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in THAYER, NEBRASKA
From 20-SEP-18 17:54:00 to 20-SEP-18 17:54:00 (CST-6)
Location: DAVENPORT
Magnitude: 56.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm Wind in THAYER, NEBRASKA
From 20-SEP-18 17:57:00 to 20-SEP-18 17:57:00 (CST-6)
Location: HEBRON
Magnitude: 52.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A portion of a tree was downed and landed on a power line, resulting in a loss of power for part of the town.

Thunderstorm Wind in THAYER, NEBRASKA
From 20-SEP-18 18:00:00 to 20-SEP-18 18:00:00 (CST-6)
Location: BRUNING
Magnitude: 56.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Wind gusts were estimated to be near 65 MPH based on upstream measured observations and damage done to trees and some street signs in town.

Thunderstorm Wind in WEBSTER, NEBRASKA
From 20-SEP-18 16:53:00 to 20-SEP-18 16:53:00 (CST-6)
Location: RED CLOUD
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Public

Two large tree limbs were downed by wind gusts estimated to be near 60 MPH.