Following a short stretch of dry days centered around mid-month, an abrupt transition to a very wet pattern arrived in parts of South Central Nebraska between the evening hours of Thursday the 19th and early morning hours of Friday the 20th. This came in the form of two distinct rounds of thunderstorms, with the heaviest 24-hour rainfall totals targeting locations generally east of a line from Red Cloud, to Clay Center, to Osceola. Focusing on timing, the first wave of heavy rain-producing storms spread northward across eastern portions of South Central Nebraska mainly between 6 and 8 PM CDT on the 19th, with the next, more significant round focusing on the 10 PM to 1 AM CDT time frame before gradually pushing off to the east. Within these eastern counties, 24-hour rainfall amounts of 2.5 to 4 inches were common, especially across parts of Webster, Nuckolls, Clay, Fillmore and Thayer Counties. A few of the highest reported gauge readings included 4.14 inches southeast of Deweese and 4.00 inches northwest of Alexandria. As a result, extensive lowland and small creek flooding ensued, along with flooding of several county roads, some of which were closed through at least the afternoon of the 20th. The Republican River also topped minor flood stage, with the gauge near Guide Rock cresting 0.47-foot above flood stage on the morning of the 20th.
On both the synoptic and mesoscale, South Central Nebraska was primed for a heavy rainfall event, as precipitable water values climbed to around 1.5 inches within the axis of a 40 knot low-level jet. This all took place within a region of pronounced mid-upper jet divergence, located downstream from a powerful mid-level low pressure system centered in the Central Rockies. Fortunately, a substantial severe weather threat did not materialize across the local area thanks to the surface warm front and resultant low-level destabilization remaining to the south across central and south central Kansas, where several severe storms occurred along with a few tornadoes.

Heavy Rain in NUCKOLLS, NEBRASKA
From 19-MAY-11 06:00:00 to 20-MAY-11 06:00:00 (CST-6)
Location: NELSON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Storm total rainfall of 3.98 inches was reported by a NeRAIN observer.

Flood in WEBSTER, NEBRASKA
From 19-MAY-11 22:00:00 to 20-MAY-11 11:00:00 (CST-6)
Location: ROSEMONT
Flood cause: Heavy Rain
Property damage: 15.00K
Crop damage: 250.00K
Reported by: Law Enforcement

Storm total rainfall accumulations of 2 to 5 inches were reported across the area.  Water covered a few county roads, and Highway 281 south of Red Cloud also had a small area briefly covered in 3 to 4 inches of water. Lowland flooding was also reported.

Flood in CLAY, NEBRASKA
From 19-MAY-11 22:00:00 to 20-MAY-11 11:00:00 (CST-6)
Location: DEWEESE
Flood cause: Heavy Rain
Property damage: 15.00K
Crop damage: 250.00K
Reported by: Law Enforcement

Storm total rainfall accumulations of 2 to 5 inches were reported across the area.  Water covered a few county roads, and the intersection of Highways 14 and 6 also had a small area briefly covered.  Lowland flooding was also reported.

Heavy Rain in CLAY, NEBRASKA
From 19-MAY-11 06:00:00 to 20-MAY-11 06:00:00 (CST-6)
Location: CLAY CENTER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Storm total rainfall of 3.15 inches was reported by a NeRAIN observer.

Heavy Rain in FILLMORE, NEBRASKA
From 19-MAY-11 06:00:00 to 20-MAY-11 06:00:00 (CST-6)
Location: OHIOWA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Storm total rainfall of 3.66 inches was reported by a NeRAIN observer.

Heavy Rain in THAYER, NEBRASKA
From 19-MAY-11 06:00:00 to 20-MAY-11 06:00:00 (CST-6)
Location: ALEXANDRIA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Storm total rainfall of 4 inches was reported by a NeRAIN observer.

Heavy Rain in CLAY, NEBRASKA
From 19-MAY-11 06:00:00 to 20-MAY-11 06:00:00 (CST-6)
Location: FAIRFIELD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Storm total rainfall of 3.58 inches was reported by a NeRAIN observer.

Heavy Rain in WEBSTER, NEBRASKA
From 19-MAY-11 06:00:00 to 20-MAY-11 06:00:00 (CST-6)
Location: RED CLOUD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Storm total rainfall of 3.50 inches was reported by a NeRAIN observer.

Heavy Rain in CLAY, NEBRASKA
From 19-MAY-11 06:00:00 to 20-MAY-11 06:00:00 (CST-6)
Location: CLAY CENTER
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Storm total rainfall of 3.70 inches was reported by a NeRAIN observer.

Heavy Rain in NUCKOLLS, NEBRASKA
From 19-MAY-11 06:00:00 to 20-MAY-11 06:00:00 (CST-6)
Location: NELSON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Storm total rainfall of 4.12 inches was reported by a NeRAIN observer.

Heavy Rain in THAYER, NEBRASKA
From 19-MAY-11 06:00:00 to 20-MAY-11 06:00:00 (CST-6)
Location: ALEXANDRIA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Storm total rainfall of 3.60 inches was reported by a NeRAIN observer.

Heavy Rain in THAYER, NEBRASKA
From 19-MAY-11 06:00:00 to 20-MAY-11 06:00:00 (CST-6)
Location: HEBRON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Storm total rainfall of 3.26 inches was reported.

Heavy Rain in THAYER, NEBRASKA
From 19-MAY-11 06:00:00 to 20-MAY-11 06:00:00 (CST-6)
Location: BRUNING
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Storm total rainfall of 3.68 inches was reported.

Heavy Rain in WEBSTER, NEBRASKA
From 19-MAY-11 06:00:00 to 20-MAY-11 06:00:00 (CST-6)
Location: RED CLOUD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Storm total rainfall of 3 inches was reported.

Hail in THAYER, NEBRASKA
From 19-MAY-11 18:12:00 to 19-MAY-11 18:12:00 (CST-6)
Location: BRUNING
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Heavy Rain in NUCKOLLS, NEBRASKA
From 19-MAY-11 06:00:00 to 20-MAY-11 06:00:00 (CST-6)
Location: LAWRENCE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Storm total rainfall of 3.91 inches was reported by a NeRAIN observer.

Heavy Rain in CLAY, NEBRASKA
From 19-MAY-11 06:00:00 to 20-MAY-11 06:00:00 (CST-6)
Location: DEWEESE
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Storm total rainfall of 4.14 inches was reported by a NeRAIN observer.

Heavy Rain in THAYER, NEBRASKA
From 19-MAY-11 06:00:00 to 20-MAY-11 06:00:00 (CST-6)
Location: ALEXANDRIA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Storm total rainfall of 4 inches was reported by a NeRAIN observer.

Flood in NUCKOLLS, NEBRASKA
From 19-MAY-11 22:00:00 to 20-MAY-11 11:00:00 (CST-6)
Location: LAWRENCE
Flood cause: Heavy Rain
Property damage: 15.00K
Crop damage: 250.00K
Reported by: Law Enforcement

Storm total rainfall accumulations of 2 to 5 inches were reported across the area.  Water covered a few county roads, especially in the Lawrence area.  Lowland flooding was also reported.