Between the late afternoon of Sunday the 22nd and sunrise on Monday the 23rd, primarily some southern-southwestern counties in South Central Nebraska (along with briefly a few northwestern ones) endured an active episode of strong to severe thunderstorms. Within the hardest-hit southern counties (mainly Furnas/Harlan/Franklin) there were several instances of not only severe-criteria wind/hail but also narrow swaths of very heavy rain and localized flash flooding...resulting from the highest official/measured short-fuse rain totals of the 2021 convective season within the 24-county local area. On the hail/wind side of things, a few of the more notable reports (all occurring between 5:30-11:30 p.m. CDT) included: golf ball size hail in rural northwestern Buffalo County; ping pong ball size stones near Wilsonville; several instances of estimated or measured gusts of 60-70 MPH within Furnas/Harlan counties (including a few downed trees in towns such as Alma/Orleans). However, for parts of primarily Furnas, Harlan, Franklin and Webster counties, this event's signature calling card was heavy rain and localized flooding. While the majority of those four counties received modest amounts of no more than 1-2 inches, significant training of storms dumped notably higher totals between 3-7+ in narrow swaths over the course of 6-8 hours. The most significant of these heavy rain bullseyes focused along/near the Highway 136 corridor between Orleans and Oxford, where 5-7+ was common, including an unofficial automated sensor that tallied 7.13 and nearby CoCoRaHS reports of 6.22 and 6.16. Although ground-truth reports of impactful flooding/flash flooding were sparse, a resident six miles north-northwest of Orleans confirmed that School Creek spilled out of its banks overnight, inundating a nearby gravel road for several hours and encroaching within 50 feet of his home. Despite this concentrated batch of very heavy rain falling directly onto the Republican River basin, there was no firm evidence that the Republican itself flooded before excess water flushed out into Harlan County Lake. Outside of this most notable heavy rain bullseye, other impressive area rain totals included 4.76 in Alma and 3.90 near Franklin.
Breaking down event evolution/timing within South Central Nebraska: things got underway between 5-6 p.m. CDT as a large severe storm infiltrated southern Furnas County after initiating a bit earlier just west of the local area. During the same hour, another severe cell fired up slightly to its east over the Furnas/Harlan County line. Between 6-7 p.m. CDT these two storms merged over Harlan County before drifting slowly east across southern Franklin/Webster counties between 7-9 p.m. CDT. Meanwhile, during this same 7-9 p.m. CDT time frame but roughly 50-80 miles to the north-northeast, a separate area of scattered strong to severe activity briefly blossomed, primarily affecting parts of Buffalo, Sherman and Howard counties (and yielding a few hail reports) before fading away. Getting back to the original southern convection, the main concerns gradually transitioned from hail/wind to hydro/flooding between 9 p.m. and midnight CDT as a persistent, west-east oriented corridor of cell training focused along a line from Furnas through Webster counties (likely as a strengthening low level jet impinged upon the outflow/cold pool trailing from the earlier-evening storms). By midnight CDT this west-east corridor of training convection had thankfully lifted slightly north of its original position (more so along a line from Gosper through Kearney counties), ending the heavy rain threat for the night in the aforementioned places that had already been swamped with impressive amounts. Post-midnight, storms continued to percolate within portions of primarily Gosper/Phelps/Kearney/Webster/Nuckolls counties for a few to several more hours, but this activity was less intense and a bit more transient than the earlier round, keeping heavy rain and flooding concerns in check. By 5 a.m. CDT, the areal coverage of activity within southern local counties had waned considerably, with the last strong storm of the night affecting Nuckolls County before mostly-dissipating by sunrise. In the mid-upper levels, South Central Nebraska received a glancing blow of lift from a compact-but-potent shortwave trough swinging east-northeast from the Dakotas toward northern MN/southern Canada during the afternoon-evening. At the surface, the local area resided within a broad warm sector, slightly east-southeast of a weak cold front stalling out over western/north central Nebraska, and hundreds of miles south of a strong low pressure system (around 998 millibars) centered over southern Manitoba during the evening-overnight. Closer to home, the late afternoon initiation of robust storms near the Furnas County area was likely aided by modest moisture convergence focused slightly northeast of a secondary/weaker surface low (around 1004 millibars) along the CO/KS border. All in all, the mesoscale environment proved rather supportive of severe storms and transient supercell structures, with late afternoon parameters featuring 2000-3000 J/kg mixed layer CAPE and around 40 knots of deep-layer wind shear.

Heavy Rain in HARLAN, NEBRASKA
From 22-AUG-21 16:00:00 to 22-AUG-21 23:00:00 (CST-6)
Location: OXFORD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

An unofficial personal weather station measured 7.13 of rain between 5 p.m. and midnight CDT.

Heavy Rain in HARLAN, NEBRASKA
From 22-AUG-21 16:00:00 to 22-AUG-21 23:00:00 (CST-6)
Location: ORLEANS
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A CoCoRaHS observer measured 6.22 of rain between 5 p.m. and midnight CDT.

Heavy Rain in HARLAN, NEBRASKA
From 22-AUG-21 16:00:00 to 22-AUG-21 23:00:00 (CST-6)
Location: STAMFORD
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A CoCoRaHS observer measured 6.16 of rain between 5 p.m. and midnight CDT.

Heavy Rain in HARLAN, NEBRASKA
From 22-AUG-21 16:00:00 to 22-AUG-21 23:00:00 (CST-6)
Location: ALMA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

An unofficial personal weather station measured 4.76 of rain between 5 p.m. and midnight CDT.

Flash Flood in HARLAN, NEBRASKA
From 22-AUG-21 21:00:00 to 23-AUG-21 03:15:00 (CST-6)
Location: OXFORD
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 3.00M
Reported by: Public

Radar estimates and local mesonet/CoCoRaHS stations confirmed a corridor of rainfall amounts from 4 to over 7 inches across this Flash Flood Warning area. The highest measured rainfall amount was 7.13 inches, recorded by a mesonet station located six miles east-southeast of Oxford, with most of this rain falling between 8-11 p.m. CDT.  A resident located six miles north-northwest of Orleans reported that School Creek flooded and covered at least one gravel road during the early morning hours...with water getting within 50 feet of his home. The initially-issued Flash Flood Warning was replaced by an Areal Flood Warning that lasted several more hours, as water gradually receded through the morning.

Heavy Rain in FRANKLIN, NEBRASKA
From 22-AUG-21 17:00:00 to 22-AUG-21 23:00:00 (CST-6)
Location: FRANKLIN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

A CoCoRaHS observer measured 3.90 of rain between 6 p.m. and midnight CDT.

Hail in FURNAS, NEBRASKA
From 22-AUG-21 16:46:00 to 22-AUG-21 16:46:00 (CST-6)
Location: HOLLINGER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in FURNAS, NEBRASKA
From 22-AUG-21 16:50:00 to 22-AUG-21 16:50:00 (CST-6)
Location: WILSONVILLE
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Thunderstorm Wind in FURNAS, NEBRASKA
From 22-AUG-21 16:57:00 to 22-AUG-21 17:00:00 (CST-6)
Location: HENDLEY
Magnitude: 62.00 MG
Property damage: 150.00K
Crop damage: 3.00M
Reported by: Storm Chaser

A handheld anemometer measured gusts of 68 and 71 MPH approximately one mile southwest of Hendley. A trained spotter located four miles west of Beaver City estimated wind gusts near 65 MPH.

Hail in FURNAS, NEBRASKA
From 22-AUG-21 17:04:00 to 22-AUG-21 17:04:00 (CST-6)
Location: HENDLEY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: County Official

Hail in FURNAS, NEBRASKA
From 22-AUG-21 17:31:00 to 22-AUG-21 17:31:00 (CST-6)
Location: HOLLINGER
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in HARLAN, NEBRASKA
From 22-AUG-21 17:38:00 to 22-AUG-21 17:38:00 (CST-6)
Location: ORLEANS
Magnitude: 56.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Tree damage was reported on the north side of town. Wind gusts estimate based on nearby mesonet measurement.

Thunderstorm Wind in HARLAN, NEBRASKA
From 22-AUG-21 17:35:00 to 22-AUG-21 17:35:00 (CST-6)
Location: STAMFORD
Magnitude: 56.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A wind gust of 65 MPH was recorded by a mesonet station located five miles northeast of Stamford.

Hail in BUFFALO, NEBRASKA
From 22-AUG-21 18:55:00 to 22-AUG-21 18:55:00 (CST-6)
Location: PLEASANTON
Magnitude: 1.75 
Property damage: 25.00K
Crop damage: 250.00K
Reported by: Public

Hail in SHERMAN, NEBRASKA
From 22-AUG-21 19:09:00 to 22-AUG-21 19:09:00 (CST-6)
Location: ASHTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Thunderstorm Wind in HARLAN, NEBRASKA
From 22-AUG-21 20:01:00 to 22-AUG-21 20:01:00 (CST-6)
Location: ALMA
Magnitude: 56.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Two trees were reported blown down in Alma.

Hail in FRANKLIN, NEBRASKA
From 22-AUG-21 21:00:00 to 22-AUG-21 21:00:00 (CST-6)
Location: FRANKLIN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm Wind in HARLAN, NEBRASKA
From 22-AUG-21 22:30:00 to 22-AUG-21 22:30:00 (CST-6)
Location: RAGAN
Magnitude: 52.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A wind gust of 60 MPH was recorded by a mesonet station located four miles east of Ragan.

Thunderstorm Wind in HARLAN, NEBRASKA
From 22-AUG-21 19:53:00 to 22-AUG-21 19:53:00 (CST-6)
Location: ORLEANS
Magnitude: 55.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A wind gust of 63 MPH was recorded by a mesonet station located six miles northwest of Orleans.