Thunderstorms developed early this Wednesday afternoon and evening, and predominantly produced tornadoes and flash flooding. With no cap in place, scattered thunderstorms began developing as early as the noon hour over north central Kansas. Most storms rapidly became supercellular. These supercells rapidly lifted north into south central Nebraska and began producing severe weather by 330 p.m. CDT. Most of the tornadoes occurred over Nuckolls and Thayer counties. One tornado did occur over Adams county and a brief spin-up also occurred over Hall county. Eventually, an MCS developed. The leading edge of the cold pool becoming stationary. New storms repeatedly developed over north central Kansas and lifted northeast along the boundary, through Nuckolls and Thayer counties and further downstream into southeastern Nebraska. Cell training produced a swath of 5-11 inches of rain over portions of Nuckolls and Thayer counties. The highest amount reported was 10.91 inches just west of Hebron. This amount of rainfall in 24 hours typically occurs once in 1,000 years at any given location, or stated another way, has a .1% chance of occurrence in a given 24 hour period. Cooperative observers in Hebron and Superior reported 8.59 and 7.13 inches, respectively. These were the highest 24-hour rainfall amounts ever recorded at these locations, dating back to 1893. Flash flooding damaged roads and some bridges were washed out. U.S. Highways 81 and 136 were closed for a time due to the flooding.
A complex low pressure system extended from the Canadian Prairies into the western United States. These storms developed in the warm sector, far away from any discernible surface boundaries. However, an axis of confluence was present over north central Kansas. A deep upper-level trough was over the western U.S., with a ridge over the East. In the southwest flow between these features, a shortwave trough was lifting through the Central Plains. These storms formed in the southeast quadrant of the associated vorticity maximum. Around the time thunderstorms developed, temperatures were in the lower 70s with dewpoints in the lower 60s, resulting in low cloud bases. Even at mid-afternoon, cloud bases were only 2000-2500 feet. The surface conditions and mid-level lapse rates of 7 degrees C/km resulted in SBCAPE around 1500 J/kg. Deep layer shear was only 25-30 knots. However, low-level wind fields were strong with 40-45 knots at 850 mb. This resulted in large hodographs with 0-1 km SRH values of 200-250 m2/s2, and 0-3 km SRH of 250-300 m2/s2. Combined with low cloud bases, this created a favorable environment for supercells and tornadoes.

Tornado in NUCKOLLS, NEBRASKA
From 06-MAY-15 15:38:00 to 06-MAY-15 15:54:00 (CST-6)
Location: BOSTWICK
Tornado F-scale: EF1
Property damage: 250.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This tornado touched down between Bostwick and Superior, and was rated an EF1 with an estimated peak wind speed of 100 MPH. Trees were damaged, pivots were overturned and power poles were snapped. A home northwest of Superior sustained porch damage.

Tornado in THAYER, NEBRASKA
From 06-MAY-15 16:12:00 to 06-MAY-15 16:19:00 (CST-6)
Location: DESHLER
Tornado F-scale: EF2
Property damage: 1.50M
Crop damage: 0.00K
Reported by: NWS Storm Survey

This is a continuation of the tornado that touched down west-northwest of Webber in Jewell County, KS, traveling northeast through the very northwest corner of Republic County, KS, before entering Nebraska near the town of Hardy in Nuckolls County. It continued traveling northeast into Thayer County, lifting northwest of Deshler. This tornado was rated an EF2, with an estimated peak wind speed of 122 MPH. EF2 damage was noted in both Jewell County, KS and Nuckolls County, NE.
Damage along this tornado path included numerous pivots overturned and snapped power poles. There was a large amount of tree damage noted. In addition, in Thayer County, grain bins and outbuildings were destroyed, and irrigation piping was strewn across a road.

Tornado in NUCKOLLS, NEBRASKA
From 06-MAY-15 15:58:00 to 06-MAY-15 16:12:00 (CST-6)
Location: HARDY
Tornado F-scale: EF2
Property damage: 1.50M
Crop damage: 0.00K
Reported by: NWS Storm Survey

This is a continuation of the tornado that touched down west-northwest of Webber in Jewell County, KS, traveling northeast through the very northwest corner of Republic County, KS, before entering Nebraska near the town of Hardy in Nuckolls County. It continued traveling northeast into Thayer County, lifting northwest of Deshler. This tornado was rated an EF2, with an estimated peak wind speed of 122 MPH. EF2 damage was noted in both Jewell County, KS and Nuckolls County, NE.
Damage along this tornado path included numerous pivots overturned and snapped power poles. There was a large amount of tree damage noted. In addition, in Nuckolls County, grain bins and outbuildings were destroyed. One home sustained chimney and siding damage, while another home lost a large section of its roof.

Flash Flood in NUCKOLLS, NEBRASKA
From 06-MAY-15 18:00:00 to 07-MAY-15 02:00:00 (CST-6)
Location: HARDY
Flood cause: Heavy Rain
Property damage: 500.00K
Crop damage: 2.50M
Reported by: Emergency Manager

A swath of 5 to 9 inches of rain, with locally higher amounts, was reported primarily across the southeastern half of the county. The Republican River along the southern edge of the county was flooded. Numerous bridges and many miles of county roads were damaged by the flooding.

Flash Flood in THAYER, NEBRASKA
From 06-MAY-15 19:00:00 to 07-MAY-15 03:00:00 (CST-6)
Location: DAVENPORT
Flood cause: Heavy Rain
Property damage: 1.50M
Crop damage: 2.50M
Reported by: Emergency Manager

Central portions of Thayer County was the hardest hit in the NWS Hastings coverage area. A swath of 5 to 9 inches of rain, with locally higher amounts of 10 to 11 inches, was reported across the the county. Portions of Highways 81, 136 and 53 were closed for a period of time during the evening. In Hebron, a bridge was washed out, reducing the access to the local hospital and nursing/assisted living facilities down to just one road. In Deshler, water at least 6 inches deep resulted in the evacuation of 6 homes as well as a nursing home. A total of 43 residents were taken to a shelter at the local high school. At least 4 bridges and many miles of county roads were damaged by the flooding.

Flash Flood in FILLMORE, NEBRASKA
From 06-MAY-15 19:30:00 to 07-MAY-15 03:30:00 (CST-6)
Location: SHICKLEY
Flood cause: Heavy Rain
Property damage: 500.00K
Crop damage: 2.50M
Reported by: Emergency Manager

A swath of 5 to 9 inches of rain, with locally higher amounts, was reported primarily across the far southeastern corner of the county. County roads and bridges were likely damaged by the flooding.

Tornado in THAYER, NEBRASKA
From 06-MAY-15 17:04:00 to 06-MAY-15 17:19:00 (CST-6)
Location: CHESTER
Tornado F-scale: EF2
Property damage: 1.00M
Crop damage: 0.00K
Reported by: NWS Storm Survey

This is a continuation of the tornado that touched down in the Scandia area of Republic County, KS.  This tornado was rated an EF2, with an estimated peak wind speed of 120 MPH. The strongest and widest portion of this tornado occurred in Republic County, KS.
In the Thayer County, NE, portion of this tornado, trees were damaged and pivots were overturned. Power poles and grain bins were damaged. One home southeast of Hebron had its roof partially removed. This tornado crossed Highway 81 approximately 6 miles south of Hebron.

Tornado in THAYER, NEBRASKA
From 06-MAY-15 16:26:00 to 06-MAY-15 16:30:00 (CST-6)
Location: DAVENPORT
Tornado F-scale: EF0
Property damage: 500.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This tornado was rated an EF0, with an estimated peak wind speed of 80 MPH. Damage from this tornado included a few overturned train cars west of Carleton and overturned irrigation pivots.

Hail in FRANKLIN, NEBRASKA
From 06-MAY-15 14:43:00 to 06-MAY-15 14:43:00 (CST-6)
Location: HILDRETH
Magnitude: 1.50 
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Public

Heavy Rain in FILLMORE, NEBRASKA
From 06-MAY-15 06:00:00 to 07-MAY-15 06:00:00 (CST-6)
Location: OHIOWA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A 24 hour storm total rainfall amount of 6.40 inches was reported.

Heavy Rain in NUCKOLLS, NEBRASKA
From 06-MAY-15 06:00:00 to 07-MAY-15 06:00:00 (CST-6)
Location: HARDY
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A 24 hour storm total rainfall amount of 8.20 inches was reported.

Heavy Rain in NUCKOLLS, NEBRASKA
From 06-MAY-15 06:00:00 to 07-MAY-15 06:00:00 (CST-6)
Location: SUPERIOR
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

A 24 hour storm total rainfall amount of 7.13 inches was reported. In 123 years of records dating back to 1893, this was the highest 24 hour rainfall on record.

Heavy Rain in THAYER, NEBRASKA
From 06-MAY-15 06:00:00 to 07-MAY-15 06:00:00 (CST-6)
Location: HEBRON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

A 24 hour storm total rainfall amount of 8.59 inches was reported. In 123 years of records dating back to 1893, this was the highest 24 hour rainfall on record.

Heavy Rain in THAYER, NEBRASKA
From 06-MAY-15 06:00:00 to 07-MAY-15 06:00:00 (CST-6)
Location: BYRON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A 24 hour storm total rainfall amount of 8.78 inches was reported.

Heavy Rain in THAYER, NEBRASKA
From 06-MAY-15 06:00:00 to 07-MAY-15 06:00:00 (CST-6)
Location: CARLETON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A 24 hour storm total rainfall amount of 6.17 inches was reported.

Heavy Rain in THAYER, NEBRASKA
From 06-MAY-15 06:00:00 to 07-MAY-15 06:00:00 (CST-6)
Location: HEBRON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A 24 hour storm total rainfall amount of 10.91 inches was reported.

Heavy Rain in NUCKOLLS, NEBRASKA
From 06-MAY-15 06:00:00 to 07-MAY-15 06:00:00 (CST-6)
Location: RUSKIN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A 24 hour storm total rainfall amount of 7.70 inches was reported.

Heavy Rain in THAYER, NEBRASKA
From 06-MAY-15 06:00:00 to 07-MAY-15 06:00:00 (CST-6)
Location: GILEAD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A 24 hour storm total rainfall amount of 5.50 inches was reported.

Heavy Rain in THAYER, NEBRASKA
From 06-MAY-15 06:00:00 to 07-MAY-15 06:00:00 (CST-6)
Location: ALEXANDRIA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A 24 hour storm total rainfall amount of 8.30 inches was reported.

Heavy Rain in THAYER, NEBRASKA
From 06-MAY-15 06:00:00 to 07-MAY-15 06:00:00 (CST-6)
Location: CHESTER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A 24 hour storm total rainfall amount of 5.23 inches was reported.

Heavy Rain in THAYER, NEBRASKA
From 06-MAY-15 06:00:00 to 07-MAY-15 06:00:00 (CST-6)
Location: DAVENPORT
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A 24 hour storm total rainfall amount of 5.82 inches was reported.

Heavy Rain in THAYER, NEBRASKA
From 06-MAY-15 07:00:00 to 07-MAY-15 07:00:00 (CST-6)
Location: BRUNING
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

A 24 hour storm total rainfall amount of 5.10 inches was reported.

Thunderstorm Wind in CLAY, NEBRASKA
From 06-MAY-15 16:15:00 to 06-MAY-15 16:15:00 (CST-6)
Location: EDGAR
Magnitude: 65.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Wind gusts were estimated to be near 75 MPH, with tree limbs downed in town. The local fire chief reported to a radio station that a lean-to building just south of town had been destroyed.

Thunderstorm Wind in THAYER, NEBRASKA
From 06-MAY-15 16:35:00 to 06-MAY-15 16:35:00 (CST-6)
Location: HEBRON ARPT
Magnitude: 61.00 MG
Property damage: 100.00K
Crop damage: 0.00K
Reported by: AWOS

Emergency manager reported widespread tree damage, including large trees, in town.

Tornado in THAYER, NEBRASKA
From 06-MAY-15 16:28:00 to 06-MAY-15 16:31:00 (CST-6)
Location: BYRON
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

There was no damage reported with this tornado. The path was determined from video and radar information.

Tornado in HALL, NEBRASKA
From 06-MAY-15 16:45:00 to 06-MAY-15 16:45:00 (CST-6)
Location: ALDA
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

This tornado briefly touched down and was reported by a trained spotter. No damage occurred.

Tornado in ADAMS, NEBRASKA
From 06-MAY-15 15:18:00 to 06-MAY-15 15:28:00 (CST-6)
Location: ROSELAND
Tornado F-scale: EF1
Property damage: 1.50M
Crop damage: 0.00K
Reported by: NWS Storm Survey

This tornado touched down about 3 miles south of Roseland, clipping the east side of town before lifting just north-northeast of town. This tornado was rated an EF1, with an estimated peak wind speed of 110 MPH. The most widespread damage from this tornado was on the east side of town, and while several homes and outbuildings sustained damage, 2 sustained considerable damage. One of those homes slide from its foundation and another lost its entire roof structure. A large metal building with wood post frame construction was destroyed and tree damage was widespread throughout town. The tornado traveled just a few hundred feet east of Silver Lake School.