Between 4-9 p.m. CDT on this Sunday afternoon and evening, a smattering of strong to severe thunderstorms developed along and just ahead of an invading cold front, producing hail in various parts of South Central Nebraska, but especially within Polk, Nance and northeast Merrick counties in far northeast portions of the local area. Within these counties, the main event occurred between 430-630 p.m. CDT as a cluster of semi-discrete severe storms blossomed slightly ahead of the cold front and tracked east-northeast before exiting into eastern Nebraska. Polk County yielded the most hail reports, with nickel to quarter size stones reported in the Osceola and Shelby areas, and larger golf ball size stones reported in western and far northeast sections of the county. In fact, a NeRAIN observer located a few miles south-southwest of Columbus reported broken windows and roof damage in the area. Outside of this main, concentrated zone of severe storms, a combination of linear and small multicell storm structures yielded a few instances of sub-severe hail in the Ord, Red Cloud and Hubbell areas, and a lone quarter size report in Clay Center. By 9 p.m. CDT, the surface cold front had pushed through all of South Central Nebraska, ending all local thunderstorm activity for the night as convection exited Fillmore and Thayer counties to the east. Rainfall-wise, the vast majority of affected areas received well under 1.
In the mid-upper levels, forcing was provided by the southern reaches of a broad shortwave trough tracking east across the Central and especially Northern Plains, with this trough ushering in increasing west-southwest flow aloft. At the surface, the well-defined, northeast-southwest oriented cold front steadily swept through South Central Nebraska during the afternoon and evening. Ahead of the boundary, afternoon temperatures across most of the local area topped out between 75-80 F as dewpoints rose to between 50-55 F on gusty south winds. By the time storms initiated, the combination of mixed-layer CAPE values on the order of 1000 J/kg and 0-6 kilometer deep layer wind shear of 30-50 knots was plenty sufficient for large hail production.

Hail in NANCE, NEBRASKA
From 12-APR-15 15:53:00 to 12-APR-15 16:03:00 (CST-6)
Location: FULLERTON
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in POLK, NEBRASKA
From 12-APR-15 16:25:00 to 12-APR-15 16:30:00 (CST-6)
Location: OSCEOLA
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Hail in CLAY, NEBRASKA
From 12-APR-15 18:47:00 to 12-APR-15 18:47:00 (CST-6)
Location: CLAY CENTER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in POLK, NEBRASKA
From 12-APR-15 16:55:00 to 12-APR-15 16:55:00 (CST-6)
Location: SHELBY
Magnitude: 1.75 
Property damage: 150.00K
Crop damage: 0.00K
Reported by: Social Media

In addition, a nearby NeRAIN observer reported some broken windows and roof damage in the extreme northeast Polk County area.

Hail in POLK, NEBRASKA
From 12-APR-15 16:58:00 to 12-APR-15 16:58:00 (CST-6)
Location: SWEDEHOME
Magnitude: 1.75 
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Public

Hail in POLK, NEBRASKA
From 12-APR-15 16:41:00 to 12-APR-15 16:41:00 (CST-6)
Location: SHELBY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Pea sized hail covered the ground, with some quarter sized hail mixed in.