Between the evening of Sunday the 13th and the pre-dawn hours of Monday the 14th, a few small clusters of severe thunderstorms pressed southward across far western portions of South Central Nebraska, yielding several reports of severe-criteria hail and winds within Dawson, Gosper and Furnas counties, along with very-localized heavy rainfall in excess of 3 inches. As for hail, the largest reported stones up to ping pong size fell in Cozad and near Johnson Lake, with half dollar size hail reported in Gothenburg and near Holbrook. As for severe winds, a mesonet station near Cambridge measured a peak of 68 MPH and a storm chaser near Arapahoe clocked a 65 MPH gust. Several tree branches were downed in Cambridge, some up to 6-8 inches in diameter. Rainfall-wise, most areas affected by this convection received less than 2, but localized pockets of all three affected counties tallied 3 or more, including 3.72 in Cozad. However, any known flooding impacts were fairly minimal.
Timing-wise, the first severe storms of the night to affect the local area drifted into Dawson County from the north between 9:00-10:30 p.m. CDT, including an embedded supercell in the western half of the county. For the next several hours, this storm expanded into a small-scale severe cluster as it trudged slowly southward through Gosper and Furnas counties, eventually weakening/dissipating near the KS border around 2 a.m. CDT. Meanwhile, another cluster of strong to perhaps marginally severe storms redeveloped over Dawson County between 1:30-3:30 a.m. CDT, but the only ground-truth report consisted of penny size hail at Willow Island. By 3:30 a.m. CDT the severe weather threat had ended, with only weak convection gradually fading thereafter.
Meteorologically, this was a fairly classic case of a weakly forced but moderately unstable late-summer severe storm setup. In the mid-upper levels, flow was from the west-northwest, with a fairly subtle shortwave trough moving into the region. At the surface, a weak cold front was draped through north central and western Nebraska during the afternoon, sparking the initial severe convection of the day. Eventually, these storms propagated southward into the local area around dark, sustained into the night by considerable instability and a modest southwesterly low level jet of 25-30 knots (evident at 850 millibars). During the majority of the later evening, most-unstable CAPE was around 2000 J/kg and effective deep-layer wind shear averaged 30-40 knots.

Hail in DAWSON, NEBRASKA
From 13-AUG-17 20:33:00 to 13-AUG-17 20:33:00 (CST-6)
Location: SUMNER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in DAWSON, NEBRASKA
From 13-AUG-17 20:58:00 to 13-AUG-17 21:08:00 (CST-6)
Location: GOTHENBURG
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in DAWSON, NEBRASKA
From 13-AUG-17 21:19:00 to 13-AUG-17 21:23:00 (CST-6)
Location: COZAD
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Hail in GOSPER, NEBRASKA
From 13-AUG-17 22:00:00 to 13-AUG-17 22:00:00 (CST-6)
Location: JOHNSON RES
Magnitude: 1.50 
Property damage: 25.00K
Crop damage: 150.00K
Reported by: Public

Thunderstorm Wind in GOSPER, NEBRASKA
From 13-AUG-17 23:04:00 to 13-AUG-17 23:04:00 (CST-6)
Location: ELWOOD
Magnitude: 56.00 EG
Property damage: 25.00K
Crop damage: 250.00K
Reported by: Storm Chaser

Wind gusts were estimated to be near 65 MPH.

Thunderstorm Wind in FURNAS, NEBRASKA
From 13-AUG-17 23:22:00 to 13-AUG-17 23:22:00 (CST-6)
Location: CAMBRIDGE
Magnitude: 51.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Thunderstorm Wind in FURNAS, NEBRASKA
From 13-AUG-17 23:24:00 to 13-AUG-17 23:24:00 (CST-6)
Location: ARAPAHOE
Magnitude: 56.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Thunderstorm Wind in FURNAS, NEBRASKA
From 13-AUG-17 23:31:00 to 13-AUG-17 23:31:00 (CST-6)
Location: CAMBRIDGE
Magnitude: 59.00 MG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Mesonet

A storm chaser reported several downed tree branches in Cambridge, a few were up to 6 to 8 inches in diameter.

Hail in FURNAS, NEBRASKA
From 13-AUG-17 23:35:00 to 13-AUG-17 23:35:00 (CST-6)
Location: HOLBROOK
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Hail in FURNAS, NEBRASKA
From 14-AUG-17 00:22:00 to 14-AUG-17 00:22:00 (CST-6)
Location: WILSONVILLE
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Hail in DAWSON, NEBRASKA
From 14-AUG-17 01:22:00 to 14-AUG-17 01:22:00 (CST-6)
Location: WILLOW IS
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement