Although only a small fraction of South Central Nebraska experienced severe weather on this Thursday evening, the one severe storm that formed was one of the most intense individual storms of the mid-to-late summer within the area. Rapidly evolving from a multicell cluster to a brief high-precipitation supercell, this storm packed quite a punch, causing considerable wind damage as it pushed along the Nebraska and Kansas border mainly between 9 PM and 1030 PM CDT, impacting southeastern Webster and especially southern Nuckolls Counties. The community of Superior and its immediate vicinity bore the brunt of severe weather, with estimated winds to at least 80 MPH causing extensive tree and crop damage and some structural damage as well. Some of this structural damage in Superior included a metal combination storage and residence building having much of its roof and one wall ripped away. In addition to damaging winds, dime to quarter size hail also affected the Superior area along with torrential rainfall estimated to around 2.5 inches that resulted in considerable street flooding. As this storm moved just east of the Superior area toward southwestern Thayer County, it rapidly started to weaken and dissipate. Although additional thunderstorms rumbled across mainly the southern-most row of South Central Nebraska counties well into the early morning hours on the 22nd, none of these became severe.
This storm rapidly intensified around 9 PM CDT, evolving from a weak and narrow line of convection that had been drifting east along the state line for the previous few hours. This area of convection was largely detached from more widespread multicell storm activity ongoing at least 50-80 miles to the south in Kansas. The rapid intensification into a supercell was likely due to a combination of factors, including the encountering of a more unstable and less-capped airmass in the vicinity of a surface warm front. Mesoscale severe weather parameters around this time featured only marginal deep-layer vertical wind shear around 30 knots, but significant mixed-layer CAPE of 3000-4000 J/kg. Aloft, synoptic forcing was weak, with only subtle mid level disturbances passing through weak to modest quasi-zonal flow. This was a typical summer pattern for South Central Nebraska, with the region positioned along the interface between a broad upper level ridge across the southern states, and faster westerly flow across the northern tier of the nation.

Hail in NUCKOLLS, NEBRASKA
From 21-JUL-11 21:05:00 to 21-JUL-11 21:05:00 (CST-6)
Location: SUPERIOR
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in NUCKOLLS, NEBRASKA
From 21-JUL-11 21:15:00 to 21-JUL-11 21:15:00 (CST-6)
Location: SUPERIOR
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Thunderstorm Wind in NUCKOLLS, NEBRASKA
From 21-JUL-11 20:40:00 to 21-JUL-11 21:10:00 (CST-6)
Location: SUPERIOR ARPT
Magnitude: 70.00 EG
Property damage: 300.00K
Crop damage: 5.00M
Reported by: Fire Department/Rescue

Wind gusts were estimated to reach as high as 80 MPH for an extended period of time near Superior and south to the Nebraska and Kansas state line.  There were reports of widespread minor to extensive tree and crop damage around the area, with a few tree limbs even landing on vehicles and homes in Superior.  At least 4 to 5 area outbuildings and sheds were damaged or destroyed, as well as a couple of grain bins, and 2 irrigation pivots were overturned.