A few small storms produced low-end severe hail during the late afternoon and early evening hours on this Tuesday. Late in the afternoon, a few small primarily single-cell low-top thunderstorms began forming over north central Kansas. Around 6 PM CST, two of these storms progressed across the state line and into south central Nebraska. They were joined by a few other storms through 9 PM. These storms produced small (sub-severe) hail in several locations along the Webster-Franklin County border. However, just after 8 PM, severe hail was reported between the towns of Campbell and Riverton. The largest hail observed was the size of half dollars. The tops of these storms were not much higher than 30,000 ft. Between 9 and 11 PM, the coverage of storms increased in an east-west broken line across south central Nebraska, just north of the state line. The result was a transition to multi-cell convective mode. In addition, a small line segment of storms was approaching the western end of this line from northwest Kansas. The east-west oriented line gradually lifted north while the Kansas line segment moved in from the west. Other small storms initiated and/or moved in from Kansas, as a result of the low-level jet, with all of this activity eventually congealing into a mostly sub-severe mesoscale convective system. There was a single report of 1 inch hail in the town of Lexington at midnight. Between midnight and 3:30 AM on the 10th, an embedded line segment of storms became oriented from southwest to northeast along the northern border of Hamilton County and it moved very little. This resulted in a narrow corridor of heavy rainfall between 2.50 and 3.25.
All of this thunderstorm activity formed along and north of a quasi-stationary front near the Nebraska-Kansas border, and ahead of a low pressure system making its way through the Desert Southwest. In the upper-levels, the flow was from the southwest, with a ridge over the Mississippi Valley and a low advancing slowly through Arizona. When the initial storms developed, the environment was characterized by temperatures in the upper 70s with dewpoints in the middle to upper 50s. Mid-level lapse rates were poor, resulting in MLCAPE around 1000 J/kg. As the boundary layer stabilized, MUCAPE remained no greater than 1000 J/kg. Effective deep layer shear was 25 to 30 kts.

Hail in FRANKLIN, NEBRASKA
From 09-MAY-17 20:15:00 to 09-MAY-17 20:15:00 (CST-6)
Location: RIVERTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in WEBSTER, NEBRASKA
From 09-MAY-17 20:27:00 to 09-MAY-17 20:27:00 (CST-6)
Location: INAVALE
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in KEARNEY, NEBRASKA
From 09-MAY-17 23:15:00 to 09-MAY-17 23:15:00 (CST-6)
Location: MINDEN
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Heavy Rain in HAMILTON, NEBRASKA
From 10-MAY-17 00:00:00 to 10-MAY-17 04:00:00 (CST-6)
Location: HORDVILLE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A rainfall total of 3.25 inches fell between 1 and 5 am CDT.

Hail in DAWSON, NEBRASKA
From 10-MAY-17 00:00:00 to 10-MAY-17 00:00:00 (CST-6)
Location: LEXINGTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public