Severe thunderstorms, some which produced heavy rain and flash flooding, tracked across eastern Nebraska for the second consecutive day.  The storms were focused along two boundaries.  One was a cold front that dropped south from northeast Nebraska and the other was a dry-line type front that was pushing east northeast from south central Nebraska and northern Kansas.  Temperatures and dew points in southeast Nebraska ahead of both fronts were in the mid to upper 70s and lower 60s respectively, while temperatures were in the lower 60s behind the cold front and dew point temperatures west of the dry-line were in the mid 40s to around 50.  A large upper low in southwest Nebraska caused surface low pressure to deepen over southwest Nebraska/north central Kansas which caused much of the activity in Nebraska to track to the north or northwest, but the interacting boundaries caused varying movements later in the event with some back-building producing heavy rain and low level shear caused a possible but unconfirmed short-lived weak tornado west northwest of Seward.

Flood in BUTLER, NEBRASKA
From 12-MAY-11 22:11:00 to 13-MAY-11 02:15:00 (CST-6)
Location: SURPRISE
Flood cause: Heavy Rain
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Official NWS Observations

Rainfall of around 3 inches in several hours caused flooding along the upper reaches of the Big Blue River near Surprise.  The river near Surprise crested at little over 8 feet a little before midnight CST on the 12th, flood stage is 7 feet.  Flooding mainly affected agricultural lowlands but also flooded a county road or two in the area.

Hail in PLATTE, NEBRASKA
From 12-MAY-11 17:08:00 to 12-MAY-11 17:08:00 (CST-6)
Location: ROSENBURG
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Pea to quarter-size hail covered the ground west of Columbus.

Hail in SALINE, NEBRASKA
From 12-MAY-11 18:04:00 to 12-MAY-11 18:04:00 (CST-6)
Location: TOBIAS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Hail in LANCASTER, NEBRASKA
From 12-MAY-11 18:25:00 to 12-MAY-11 18:25:00 (CST-6)
Location: AGNEW
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Hail in GAGE, NEBRASKA
From 12-MAY-11 18:30:00 to 12-MAY-11 18:30:00 (CST-6)
Location: BLUE SPGS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in LANCASTER, NEBRASKA
From 12-MAY-11 19:45:00 to 12-MAY-11 19:45:00 (CST-6)
Location: MALCOLM
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Nickel-size hail fell around the Malcolm area.

Hail in GAGE, NEBRASKA
From 12-MAY-11 19:40:00 to 12-MAY-11 19:40:00 (CST-6)
Location: BLUE SPGS
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in SEWARD, NEBRASKA
From 12-MAY-11 18:58:00 to 12-MAY-11 18:58:00 (CST-6)
Location: SEWARD
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Hail in LANCASTER, NEBRASKA
From 12-MAY-11 18:50:00 to 12-MAY-11 18:50:00 (CST-6)
Location: DAVEY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in SEWARD, NEBRASKA
From 12-MAY-11 19:04:00 to 12-MAY-11 19:06:00 (CST-6)
Location: SEWARD
Magnitude: 1.75 
Crop damage: 0.00K
Reported by: Trained Spotter

Hail up to golf ball-size fell in the Seward area for several minutes.

Hail in PLATTE, NEBRASKA
From 12-MAY-11 18:56:00 to 12-MAY-11 18:56:00 (CST-6)
Location: COLUMBUS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in BUTLER, NEBRASKA
From 12-MAY-11 19:12:00 to 12-MAY-11 19:12:00 (CST-6)
Location: SURPRISE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in GAGE, NEBRASKA
From 12-MAY-11 19:31:00 to 12-MAY-11 19:42:00 (CST-6)
Location: BLUE SPGS
Magnitude: 1.25 
Crop damage: 0.00K
Reported by: Trained Spotter

Hail up to half dollar-size fell in the Wymore area for at least 10 minutes.

Flash Flood in PLATTE, NEBRASKA
From 12-MAY-11 19:41:00 to 12-MAY-11 21:10:00 (CST-6)
Location: PLATTE CENTER
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Heavy rain cause brief flash-flooding of at least one road near Platte Center.  Rainfall at the Loup Power Plant northeast of Columbus totaled over 3 inches from the storms this night, and some street flooding was also reported in Columbus. Any damage due to flooding was apparently minimal.

Flash Flood in BUTLER, NEBRASKA
From 12-MAY-11 20:11:00 to 12-MAY-11 22:11:00 (CST-6)
Location: SURPRISE
Flood cause: Heavy Rain
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy rain, around 3 inches in a few hours in the Surprise area, caused the Big Blue River and some small tributaries to flood in the Surprise area.  The flooding mainly affected agricultural lowlands, but a few roads were also flooded for a bit.

Hail in THURSTON, NEBRASKA
From 12-MAY-11 16:00:00 to 12-MAY-11 16:15:00 (CST-6)
Location: MACY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail up to 1 inch in diameter fell for at least 15 to 20 minutes northwest of Decatur.

Hail in LANCASTER, NEBRASKA
From 12-MAY-11 17:25:00 to 12-MAY-11 17:35:00 (CST-6)
Location: LANCASTER
Magnitude: 1.75 
Crop damage: 0.00K
Reported by: Trained Spotter

Hail up to golf ball-size fell across mainly southeast Lincoln, with 1 inch hail reported near 70th and Pioneers, 1.5 inch hail near 40th and Old Cheney, and 1.75 inch hail near 48th and Highway 2.

Flash Flood in SAUNDERS, NEBRASKA
From 12-MAY-11 21:22:00 to 12-MAY-11 23:22:00 (CST-6)
Location: CERESCO
Flood cause: Heavy Rain
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Heavy rain, estimated at 2 to 3 inches in a few hours, caused flash flooding which briefly closed at least one county road near Ceresco.

Hail in JEFFERSON, NEBRASKA
From 12-MAY-11 17:25:00 to 12-MAY-11 17:25:00 (CST-6)
Location: POWELL
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Rain in BUTLER, NEBRASKA
From 12-MAY-11 18:11:00 to 12-MAY-11 20:11:00 (CST-6)
Location: SURPRISE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Rainfall of close to 3 inches fell in a few hour period in the Surprise area.  The rain caused flash flooding along parts of the upper reaches of the Big Blue River.

Hail in LANCASTER, NEBRASKA
From 12-MAY-11 20:08:00 to 12-MAY-11 20:08:00 (CST-6)
Location: ARROW ARPT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Dime to quarter-size hail was reported near Cornhusker and I80.

Flash Flood in SAUNDERS, NEBRASKA
From 12-MAY-11 21:22:00 to 12-MAY-11 22:22:00 (CST-6)
Location: MEAD
Flood cause: Heavy Rain
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Heavy rain, estimated at between 2 and 3 inches, caused a brief closure of Highway 92 between Mead and Yutan due to water and mud over the road.

Hail in SARPY, NEBRASKA
From 12-MAY-11 21:05:00 to 12-MAY-11 21:05:00 (CST-6)
Location: GRETNA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Hail in DOUGLAS, NEBRASKA
From 12-MAY-11 21:17:00 to 12-MAY-11 21:17:00 (CST-6)
Location: OMAHA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Quarter-size hail fell near 107th and Ida Streets in far northwest Omaha.

Thunderstorm Wind in BUTLER, NEBRASKA
From 12-MAY-11 19:50:00 to 12-MAY-11 19:50:00 (CST-6)
Location: GARRISON
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorms winds estimated at around 60 mph downed some 2 to 3 inch in diameter tree branches near Garrison.

Hail in DOUGLAS, NEBRASKA
From 12-MAY-11 21:35:00 to 12-MAY-11 21:35:00 (CST-6)
Location: GIBSON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Reported near 27th and Mason Streets.