Serving as the opening act to an active several days of severe weather, this Tuesday evening featured a cluster of hail-producing supercell storms within eastern portions of the area, primarily affecting Hamilton, York and Polk Counties. There were several reports of nickel to quarter size hail, with the largest stones up to ping pong ball size reported near Aurora, York and Gresham. The initial development, which was not severe, occurred between 630 PM and 8 PM CDT as a lone storm tracked northeast through parts of Franklin and Adams Counties. Then between 830 and 930 PM, this initial storm intensified across northern Clay County, while nearby, other supercells developed over Hamilton and Polk Counties. This localized supercell cluster exited east out of York and Polk Counties by 1130 PM CDT, ending all storm activity for the night within the 24-county area. In the mid and upper levels, this event was driven by the passage of a rather subtle shortwave trough within a west-southwest flow regime. At the surface, the initial late afternoon storm flared up near a surface trough axis, ahead of a cold front in western and north central Nebraska. As storms intensified during the evening, they were aided by a modest low level jet accelerating to around 35 knots at 850 millibars. Around the time of the largest hail reports, the mesoscale environment featured around 40 knots of 0-6 km vertical wind shear and 2500 J/kg mixed-layer CAPE.

Hail in CLAY, NEBRASKA
From 01-MAY-12 20:25:00 to 01-MAY-12 20:25:00 (CST-6)
Location: SUTTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in HAMILTON, NEBRASKA
From 01-MAY-12 20:29:00 to 01-MAY-12 20:31:00 (CST-6)
Location: AURORA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Hail in YORK, NEBRASKA
From 01-MAY-12 21:15:00 to 01-MAY-12 21:15:00 (CST-6)
Location: YORK
Magnitude: 1.50 
Property damage: 25.00K
Crop damage: 500.00K
Reported by: Public

Hail in HAMILTON, NEBRASKA
From 01-MAY-12 20:51:00 to 01-MAY-12 20:51:00 (CST-6)
Location: AURORA
Magnitude: 1.50 
Property damage: 25.00K
Crop damage: 500.00K
Reported by: Broadcast Media

Hail in POLK, NEBRASKA
From 01-MAY-12 20:39:00 to 01-MAY-12 20:39:00 (CST-6)
Location: OSCEOLA
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Hail in POLK, NEBRASKA
From 01-MAY-12 20:51:00 to 01-MAY-12 20:54:00 (CST-6)
Location: SHELBY
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Hail in YORK, NEBRASKA
From 01-MAY-12 22:00:00 to 01-MAY-12 22:00:00 (CST-6)
Location: GRESHAM
Magnitude: 1.50 
Property damage: 25.00K
Crop damage: 500.00K
Reported by: COOP Observer

Hail in YORK, NEBRASKA
From 01-MAY-12 20:59:00 to 01-MAY-12 20:59:00 (CST-6)
Location: YORK
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YORK, NEBRASKA
From 01-MAY-12 21:30:00 to 01-MAY-12 21:30:00 (CST-6)
Location: WACO
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in YORK, NEBRASKA
From 01-MAY-12 21:33:00 to 01-MAY-12 21:33:00 (CST-6)
Location: BENEDICT
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YORK, NEBRASKA
From 01-MAY-12 21:43:00 to 01-MAY-12 21:43:00 (CST-6)
Location: BENEDICT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in YORK, NEBRASKA
From 01-MAY-12 21:44:00 to 01-MAY-12 21:44:00 (CST-6)
Location: BENEDICT
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public