Excessive rainfall occurred over eastern Dawson and western Buffalo counties on this Wednesday night and very early Thursday morning, with flash flooding south of Sumner. During the evening hours, numerous thunderstorms developed from near McCook to North Platte to Broken Bow to Albion. Around 9 PM CST, a separate, small cluster of thunderstorms formed over eastern Dawson county. Repeated cell development kept heavy downpours over the area until 11 PM CST. Meanwhile, the tail end of the storms to the west was progressing eastward. Between 1030 and 11 PM, more thunderstorms developed within advancing tail and formed a line from central Dawson county south into Gosper county. This line then moved across the eastern part of Dawson county and into western Buffalo county between 1130 PM and 1 AM CST. More thunderstorms formed and dropped more heavy rain over these areas between 200 and 400 AM CST. Rain gauge measurements were scarce in this rural area. On the northern gradient, where radar indicated the greatest amounts fell, a CoCoRaHS observer measured 4.30 in. This excessive rainfall resulted in a flash flood roughly 7 miles north-northwest of Overton causing significant damage to a home and totaling 3 vehicles on the property. Minor flooding also occurred on Elm Creek, and low spots were flooded along several country roads in eastern Dawson county.
During the day Wednesday, low pressure was over southern Manitoba with a slow-moving cold front extending across the Dakota's into the Nebraska Panhandle. By evening, this front had become stationary from Goodland, Kansas to North Platte to O'Neill. In the upper-levels, subtropical high pressure encompassed most of the United States. A low was off the Pacific Northwest coast, and a shortwave trough was crossing the Northern Plains and southern Canada. By daybreak, the southern tip of this trough extended into Nebraska, but winds aloft were very weak. Just before thunderstorms moved into the area, temperatures had fallen into the middle 70s and dewpoints were in the middle 60s. Mid-level lapse rates were near 7 C/km, with MUCAPE around 2000 J/kg. Deep layer shear was 30-35 kt. The low-level jet was weak (20-30 kt) but present with its northern terminus at the frontal zone.

Heavy Rain in BUFFALO, NEBRASKA
From 04-JUL-18 21:30:00 to 05-JUL-18 05:00:00 (CST-6)
Location: MILLER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A storm total rainfall amount of 3.35 inches was recorded by a mesonet site located in Miller.

Heavy Rain in DAWSON, NEBRASKA
From 04-JUL-18 21:30:00 to 05-JUL-18 05:00:00 (CST-6)
Location: SUMNER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A storm total rainfall amount of 4.30 inches was recorded by a mesonet site located 2 miles west of Miller.

Flash Flood in DAWSON, NEBRASKA
From 05-JUL-18 03:00:00 to 05-JUL-18 07:00:00 (CST-6)
Location: SUMNER
Flood cause: Heavy Rain
Property damage: 150.00K
Crop damage: 2.00M
Reported by: Emergency Manager

Heavy rain fell across the warned area, and while actual ground-truth reports were only in the 3 to 5 inch range, radar estimation and unofficial reports exceeded 6 inches in east-central Dawson County. Emergency management reported that several rural roads and at least 2 homes were affected by water. The most significant report came from a home approximately 7 miles north-northwest of Overton. This home is located at the convergence point of a couple of drainage paths, and the heavy rainfall resulted in every room having at least 2 feet of water inside. All of the appliances and furniture were destroyed, and the interior will have to be completely redone once it's dried out.

Flood in DAWSON, NEBRASKA
From 05-JUL-18 07:00:00 to 06-JUL-18 18:00:00 (CST-6)
Location: OVERTON
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 2.00M
Reported by: Emergency Manager

Heavy rain fell across portions of Dawson and Buffalo counties, and while ground-truth reports were mainly in the 3 to 5 inch range, radar estimation and an unofficial report exceeded 6 inches. Much of this water drained into the Elm Creek. The gauge, located just west of the town of Elm Creek, peaked just under 10 feet and remained above flood stage until the early evening of the 6th. At a stage of 9.5 feet, water covers County Road 56. A few other rural roads were affected. A home west of the creek near Highway 30 was affected by the excess water, and area culverts were full.

Flood in BUFFALO, NEBRASKA
From 05-JUL-18 07:00:00 to 06-JUL-18 18:00:00 (CST-6)
Location: ELM CREEK
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 2.00M
Reported by: Emergency Manager

Heavy rain fell across portions of Dawson and Buffalo counties, and while ground-truth reports were mainly in the 3 to 5 inch range, radar estimation and an unofficial report exceeded 6 inches. Much of this water drained into the Elm Creek. The gauge, located just west of the town of Elm Creek, peaked just under 10 feet and remained above flood stage until the early evening of the 6th. At a stage of 9.5 feet, water covers County Road 56. A few other rural roads were affected. A home west of the creek near Highway 30 was affected by the excess water, and area culverts were full.