On this Tuesday late afternoon and evening, thunderstorms of varying strength rumbled from southwest-to-northeast across portions of South Central Nebraska mainly between 6:00-11:30 p.m. CDT. However, the vast majority of strong to severe activity focused within a 15-30 mile wide swath centered along a line from Franklin-Blue Hill-Sutton-York. Within this corridor, there were a number of reports of large hail ranging from quarter size up to tennis ball size, with the tennis ball (2.5 inch) reports out of Harvard and Stockham. There were also several instances of ping pong ball to golf ball size stones, including in or near the following communities: Blue Hill, Sutton, Edgar and Glenvil. Finally, marginally-severe, quarter to half dollar size hail reports originated from in or near places such as: Franklin, Bladen, Clay Center, Deweese and York. Large hail was clearly the main story of the evening, as there were only a few measured strong to marginally-severe gusts of 50+ MPH, a few of which were several miles removed from obvious thunderstorm outflow and were likely associated with a weak wake low. A few of the strongest detected gusts included 58 MPH in Doniphan (unofficial mesonet) and ASOS-measured gusts of 55 and 52 MPH at Grand Island and Hastings airports, respectively.
Breaking down event evolution/timing, if anything the intensity of storms (and peak hail size) ended up being a bit surprising given the seasonably-modest and just in time nature of low-level moisture advecting northward into the area along a slow-moving surface warm front. At daybreak on the 18th, this west-east oriented front was aligned across northern Kansas, with South Central Nebraska firmly on its cool/dry side with surface dewpoints mainly only in the 20s (F). Meanwhile, in the mid-upper levels, the Central Plains resided well downstream of a large scale trough centered over the Northern Rockies. Over the course of the day, a subtle wave along the leading edges of the aforementioned parent trough entered the Central High Plains. This prompted a gradual increase in west-southwesterly, mid-upper level flow into South Central Nebraska, along with a gradual increase in south-southeasterly low-level flow, allowing slow-but-steady northward moisture transport into the lifting warm frontal zone. By late afternoon (around the time of convective initiation), a 994 millibar surface low was noted over northwest Kansas, with the attendant warm front extending into far southern Nebraska to its east, and a north-south oriented dryline trailing southward. Although still seasonably-unimpressive, surface dewpoints over the southern half of South Central Nebraska had risen well into the mid-upper 40s by this time (a surge of nearly 20 degrees over early morning values). This meager-but-sufficient low level moisture, combined with steep low-to-mid level lapse rates and convergence near the warm front/dryline intersection, was enough to initiate the first high-based storms of the afternoon over north central Kansas around 5:30 p.m. CDT. Already by 6 p.m. CDT, the first severe-warned storm of the day within South Central Nebraska had entered southern Franklin County. During the next two hours, a series of semi-discrete, strong-to-severe cells affected primarily Franklin/Webster counties. Then, between 8-10 p.m. CDT, intense elevated convection consolidated into a more cohesive line as it tracked northeastward across portions of mainly Adams/Clay/Nuckolls/Hamilton/Fillmore counties, aided by an uptick in a 40-50 knot southerly low level jet (evident at 850 millibars). Finally, between 10:00-11:30 p.m. CDT, this severe storm complex traversed York County before exiting the local area into eastern Nebraska, while other non-severe cells passed through various counties mainly along/north of Highway 92 before also departing South Central Nebraska...thus ending all local thunderstorm activity for the night. As it turned out, despite the unimpressive low level moisture magnitude, the combination of mixed-layer CAPE increasing to as high as 1000-1500 J/kg during the evening, combined with strong effective deep-layer wind shear around 50 knots, proved plenty sufficient to ignite robust updrafts.

Hail in WEBSTER, NEBRASKA
From 18-APR-23 17:28:00 to 18-APR-23 17:28:00 (CST-6)
Location: BLADEN
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in FRANKLIN, NEBRASKA
From 18-APR-23 18:24:00 to 18-APR-23 18:40:00 (CST-6)
Location: FRANKLIN
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail ranging in size from dimes to half dollars was reported along and near this path.

Hail in FRANKLIN, NEBRASKA
From 18-APR-23 18:54:00 to 18-APR-23 18:54:00 (CST-6)
Location: RIVERTON
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Hail in WEBSTER, NEBRASKA
From 18-APR-23 19:05:00 to 18-APR-23 19:35:00 (CST-6)
Location: INAVALE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Hail ranging in size from quarters to golf balls was reported along and within a few miles either side of this path.

Hail in CLAY, NEBRASKA
From 18-APR-23 19:55:00 to 18-APR-23 19:55:00 (CST-6)
Location: GLENVILLE
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Hail in CLAY, NEBRASKA
From 18-APR-23 20:00:00 to 18-APR-23 20:00:00 (CST-6)
Location: GLENVILLE
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Hail in CLAY, NEBRASKA
From 18-APR-23 20:03:00 to 18-APR-23 20:13:00 (CST-6)
Location: DEWEESE
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Hail ranging in size from quarters to golf balls was reported along and near this path.

Hail in ADAMS, NEBRASKA
From 18-APR-23 19:46:00 to 18-APR-23 19:46:00 (CST-6)
Location: PAULINE
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in NUCKOLLS, NEBRASKA
From 18-APR-23 19:57:00 to 18-APR-23 19:57:00 (CST-6)
Location: LAWRENCE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in NUCKOLLS, NEBRASKA
From 18-APR-23 20:15:00 to 18-APR-23 20:17:00 (CST-6)
Location: ANGUS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

High Wind in HALL, NEBRASKA
From 18-APR-23 19:45:00 to 18-APR-23 19:45:00 (CST-6)
Magnitude: 50.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A wind gust of 58 MPH was measured by a mesonet station on the east side of Doniphan. Only light showers were in the area at the time, and winds were likely enhanced by a weak wake low.

Hail in CLAY, NEBRASKA
From 18-APR-23 20:24:00 to 18-APR-23 20:24:00 (CST-6)
Location: HARVARD
Magnitude: 2.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Hail in CLAY, NEBRASKA
From 18-APR-23 20:16:00 to 18-APR-23 20:35:00 (CST-6)
Location: CLAY CENTER
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer

Hail up to the size of half dollars was reported along and near this path.

Hail in HAMILTON, NEBRASKA
From 18-APR-23 20:44:00 to 18-APR-23 20:49:00 (CST-6)
Location: STOCKHAM
Magnitude: 2.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Hail up to the size of tennis balls was reported in Stockham.

Hail in CLAY, NEBRASKA
From 18-APR-23 20:45:00 to 18-APR-23 20:50:00 (CST-6)
Location: SUTTON
Magnitude: 1.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Quarter to golf ball size hail was reported in Sutton.

Hail in FILLMORE, NEBRASKA
From 18-APR-23 20:47:00 to 18-APR-23 20:47:00 (CST-6)
Location: GRAFTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in YORK, NEBRASKA
From 18-APR-23 21:00:00 to 18-APR-23 21:00:00 (CST-6)
Location: LUSHTON
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Hail in YORK, NEBRASKA
From 18-APR-23 21:06:00 to 18-APR-23 21:06:00 (CST-6)
Location: YORK
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Hail in YORK, NEBRASKA
From 18-APR-23 21:52:00 to 18-APR-23 21:52:00 (CST-6)
Location: GRESHAM
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: COOP Observer