Isolated strong to severe thunderstorms flared up in eastern portions of South Central Nebraska on this Thursday evening, primarily affecting Nance, Clay and especially Fillmore counties. Although at least small hail affected various parts of these counties, including nickel size hail reported north of Genoa, all severe-criteria reports originated in Fillmore County from a supercell storm, including golf ball size stones in the Geneva area around 9 pm CDT. While hail was the main issue, strong thunderstorm winds also blew over a semi trailer just south of Geneva. In east central Fillmore County, enhanced low-level rotation was detected by radar for a short time around 930 pm CDT, but no tornadoes were reported with this storm as all tornadic activity on this night occurred east of the local area in southeast Nebraska. These storms also produced localized heavy rainfall up to around 2 inches, with the highest reported amount of 2.36 from the cooperative observer in Geneva.
Thunderstorms initiated over Clay and Nuckolls counties between 7-8 pm CDT, along a rather sharp quasi-stationary surface front aligned from southeast Nebraska into north central/west central Kansas. During this early evening time frame, winds north of the front were from the northeast while breezes south of the boundary prevailed from the south-southeast in the presence of surface dewpoints well into the 60s F, providing ample low level convergence. Between 8-11 pm CDT, a small cluster of strong to severe storms became established within Clay and Fillmore counties, with the eastern-most storm in Fillmore County organizing into a high-precipitation supercell before exiting east into Saline County. This upswing in storm coverage/severity shortly after nightfall focused along the nose of a developing 40 knot low level jet evident at 850 millibars. As the initial round of storms along the Highway 6 corridor started to weaken and depart, a separate cluster of strong thunderstorms blossomed farther north, primarily affecting Nance, northeastern Merrick and northern Polk counties between 10 pm-12 am CDT. Non-severe thunderstorms festered across these far northeast counties into the early morning hours of the 4th, but by 3 am CDT all convection had departed South Central Nebraska for the night.
The environment was ripe for supercell development by early evening, with mesoscale parameters featuring around 1500 J/kg most-unstable CAPE in the presence of around 40 knots of 0-6 kilometer deep layer wind shear. On the synoptic scale aloft, this event occurred in the presence of subtle, low amplitude shortwave troughs embedded within strengthening southwesterly flow in the mid-upper levels, downstream from a powerful closed low centered over the Central Rockies. On the following afternoon and evening of Oct. 4th, this stout low pressure system entered the Central Plains, but South Central Nebraska was narrowly spared a significant weather event thanks to a strong surface cold front and dryline pushing east of the area by late afternoon. It was a close call, however, as several damaging tornadoes raked northeast Nebraska and northwest Iowa during the late afternoon and evening of the 4th.

Hail in FILLMORE, NEBRASKA
From 03-OCT-13 20:00:00 to 03-OCT-13 20:00:00 (CST-6)
Location: GENEVA
Magnitude: 1.75 
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Public

This report of golf ball size hail was received via Facebook. The observer explicitly stated that the hail fell at 9 pm CDT.

Thunderstorm Wind in FILLMORE, NEBRASKA
From 03-OCT-13 20:22:00 to 03-OCT-13 20:22:00 (CST-6)
Location: GENEVA
Magnitude: 61.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A semi-tractor trailer was blown over one mile south of Geneva.

Hail in FILLMORE, NEBRASKA
From 03-OCT-13 20:03:00 to 03-OCT-13 20:03:00 (CST-6)
Location: GENEVA
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Hail in NANCE, NEBRASKA
From 03-OCT-13 22:05:00 to 03-OCT-13 22:05:00 (CST-6)
Location: GENOA
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Nickel size hail was falling at the time of the report.

Hail in FILLMORE, NEBRASKA
From 03-OCT-13 20:15:00 to 03-OCT-13 20:15:00 (CST-6)
Location: MILLIGAN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Hail size reported by NeRAIN observer in daily comments. Time estimated from radar data.