A long-lived supercell produced 3 weak tornadoes over Dawson county on this Friday evening. Around 2 PM CST, a north-northwest to south-southeast broken line of showers and thunderstorms developed from near Lexington to Alma and into north central Kansas. Between 2 and 430 PM CST, this line moved northeast across south central Nebraska. The strongest storms developed over Gosper and Dawson counties and moved north-northeast across Sherman and Valley counties. These storms produced some low-end severe hail (nickel to quarter size) over eastern Dawson and western Buffalo counties, and downburst winds were strong enough to knock a tree onto a lean-to south of Ord. Storms in the rest of the line rapidly weakened. Meanwhile, a lone supercell had formed over northwest Kansas. This storm moved north-northeast and crossed western Dawson county between 545 and 745 PM CST, producing three tornadoes. Two tornadoes had a maximum damage intensity of EF-1. These tornadoes were near Farnam and Cozad. The third tornado was an EF-0 west of Eddyville. The Cozad tornado was the longest with a 10-mile path. This supercell also produced severe hail from Farnam north to Gothenburg, the largest of which was the size of tennis balls in Farnam.
This was a much-anticipated day for storm chasers as the setup was classic. Deepening low pressure was over northeast Colorado, and by 6 PM CST, the pressure was down to 990 mb. This low was located along a stationary front that extended east-northeast across Nebraska. A dryline extended south from the low and a cold front was approaching from the west. The area was in the warm sector with the triple point over southwest Nebraska. As the evening progressed, the low and cold front moved into central Nebraska, with the front merging with the dryline. The flow aloft was moderately-amplified with a low over Utah, embedded within a longwave trough over the West, while a ridge was over the eastern United States. In the wake of the earlier showers and storms, within the inflow of the supercell, temperatures were in the middle 70s, with dewpoints in the middle 60s. With mid-level lapse rates 7.5-8.0 C/km, this resulted in MLCAPE around 3000 J/kg. Deep layer shear was around 40 kt. Low-level winds were strong and veered significantly with height, resulting in 0-1 km SRH between 250 and 300 m2/s2. The Supercell Composite Parameter was about 18 and the Significant Tornado Parameter was around 4.

Hail in DAWSON, NEBRASKA
From 17-MAY-19 18:52:00 to 17-MAY-19 19:05:00 (CST-6)
Location: WILLOW IS
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in DAWSON, NEBRASKA
From 17-MAY-19 18:59:00 to 17-MAY-19 18:59:00 (CST-6)
Location: GOTHENBURG
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in DAWSON, NEBRASKA
From 17-MAY-19 14:53:00 to 17-MAY-19 14:53:00 (CST-6)
Location: LEXINGTON ARPT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Tornado in DAWSON, NEBRASKA
From 17-MAY-19 18:54:00 to 17-MAY-19 19:10:00 (CST-6)
Location: COZAD
Tornado F-scale: EF1
Property damage: 900.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This tornado was witnessed by many as it formed on the east side of Cozad, where some tree damage and power poles were broken. The nearly 10-mile path weaved to the northeast across a rural landscape. One-half of a large farm machinery shed was complete destroyed and several irrigation pivots were upset, helping delineate the path. Grain bins were destroyed and tree damage was sporadic along the path. The tornado was reported to be rain-wrapped at times. The path become indiscernible as the tornado moved into the hills north of Cozad and the road network became more sparse. The estimated maximum wind speed was 100 MPH.

Hail in DAWSON, NEBRASKA
From 17-MAY-19 14:58:00 to 17-MAY-19 14:58:00 (CST-6)
Location: LEXINGTON
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Hail in DAWSON, NEBRASKA
From 17-MAY-19 15:23:00 to 17-MAY-19 15:26:00 (CST-6)
Location: OVERTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in BUFFALO, NEBRASKA
From 17-MAY-19 15:32:00 to 17-MAY-19 15:32:00 (CST-6)
Location: ELM CREEK
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Tornado in DAWSON, NEBRASKA
From 17-MAY-19 19:15:00 to 17-MAY-19 19:17:00 (CST-6)
Location: BUFFALO
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This tornado touched down west of Eddyville, and was reported to be rain wrapped as it crossed Highway 21. The path, wind speed and other information were estimated from eyewitness reports and radar data, as there are few damage indicators in the area. The estimated maximum wind speed was 85 MPH.

Thunderstorm Wind in VALLEY, NEBRASKA
From 17-MAY-19 16:15:00 to 17-MAY-19 16:15:00 (CST-6)
Location: ORD
Magnitude: 56.00 EG
Property damage: 35.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Wind gusts estimated to be near 65 MPH resulted in the destruction of a lean-to and caused a tree to fall onto a house.

Tornado in DAWSON, NEBRASKA
From 17-MAY-19 18:15:00 to 17-MAY-19 18:33:00 (CST-6)
Location: FARNAM
Tornado F-scale: EF1
Property damage: 250.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This tornado uprooted some trees, caused minor damage to some homes and completely destroyed at least one storage building. The tornado crossed Highway 23 east of Farnam, then Highway 47 northeast of Farnam before dissipating. The path became indiscernible as the storm approached rougher terrain and the road network was not viable for surveying. The estimated maximum wind speed was 100 MPH.

Hail in BUFFALO, NEBRASKA
From 17-MAY-19 15:33:00 to 17-MAY-19 15:33:00 (CST-6)
Location: ELM CREEK
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter