Arguably the most noteworthy individual thunderstorm of the 2020 convective season within this six-county North Central Kansas area rolled southward across portions of Jewell, Mitchell and mainly eastern Osborne counties on this Friday evening, highlighted by several reports of large to very large hail. Of the counties impacted by this supercell, Jewell was hardest-hit, as copious amounts of tennis ball to softball size hail stones crashed down onto areas in and near the communities of Mankato and Jewell, causing extensive damage to homes, vehicles and area crops. The hail size toned down somewhat farther south into Mitchell and Osborne counties, where limited reports included ping pong ball size stones in Cawker City and golf ball size south of Osborne. Although damaging winds were not a major player during this event, several mesonets clocked gusts of at least 40-50 MPH, and a Kansas Mesonet site near Jewell reached severe-criteria with 65 MPH. Flooding was not much of an issue, with convection staying progressive enough to keep rainfall amounts largely under one inch.
Breaking down event timing and meteorological background, this giant storm invaded northern Jewell County between 7-8 pm. CDT, having already propagated south-southwestward for roughly 90 miles since its inception in east central Nebraska about three hours prior. As it drifted southward into Mitchell County between 8-9 p.m. CDT it started merging with a much smaller, separate storm that had flared up over central Osborne County. Finally, between 9-10 p.m. CDT, the now-merged supercell cluster continued southward while exiting the local area into central Kansas, ending all local storms for the night. This was actually a fairly conditional severe weather setup for North Central Kansas, with various pros and cons for/against robust activity. In the mid-upper levels, the local area resided a fair distance south of a vigorous shortwave trough swinging across the Dakotas towards northern MN, resulting in fairly limited forcing aloft. Also working against convection (especially widespread severe) was a plume of warm mid level temperatures, with 700 millibar values of 12-14C promoting a healthy cap. On the other hand, low-level forcing was seasonably-strong, as a well-defined cold front slid southeastward into the area during the evening. Ahead of this boundary, a significantly-unstable airmass awaited, featuring temperatures in the upper 80s-low 90s F/dewpoints upper 60s-mid 70s F, yielding impressive mixed-layer CAPE up to around 4500 J/kg. This extreme instability, in the presence of sufficient deep-layer wind shear around 35 knots, clearly fostered a mesoscale environment capable of stout convection.

Thunderstorm Wind in JEWELL, KANSAS
From 14-AUG-20 19:10:00 to 14-AUG-20 19:10:00 (CST-6)
Location: JEWELL
Magnitude: 56.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

A wind gust of 65 MPH was measured by a Kansas Mesonet site located 3 miles west-northwest of Jewell.

Hail in OSBORNE, KANSAS
From 14-AUG-20 19:31:00 to 14-AUG-20 19:31:00 (CST-6)
Location: COVERT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in MITCHELL, KANSAS
From 14-AUG-20 19:50:00 to 14-AUG-20 19:50:00 (CST-6)
Location: CAWKER CITY
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Hail in JEWELL, KANSAS
From 14-AUG-20 18:40:00 to 14-AUG-20 18:40:00 (CST-6)
Location: WEBBER
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Hail in JEWELL, KANSAS
From 14-AUG-20 18:45:00 to 14-AUG-20 19:20:00 (CST-6)
Location: MANKATO
Magnitude: 4.00 
Property damage: 1.00M
Crop damage: 25.00M
Reported by: Trained Spotter

A long-lived supercell produced a substantial swath of very large hail in the Mankato and Jewell areas, with large hail produced for a significant amount of time. A public report of golf ball size hail was received at 7:45 p.m. CDT in Mankato. By 7:50 p.m. CDT, the hail size in Mankato reached a measured diameter of 4 inches, with tennis ball size hail still falling in town at 8:10 p.m. CDT. At 8:13 p.m. CDT, golf ball size hail was reported about 3 miles northwest of Randall. At 8:15 p.m. CDT, 4 inch diameter hail was reported 2 miles north of Jewell, with baseball size hail in Jewell. Significant hail damage to homes, vehicles and crops occurred in the area. As just one example, local media reported that the Jewell County EMS Director's vehicle incurred major hail damage, including a shattered windshield.

Hail in OSBORNE, KANSAS
From 14-AUG-20 20:17:00 to 14-AUG-20 20:17:00 (CST-6)
Location: OSBORNE
Magnitude: 1.75 
Property damage: 25.00K
Crop damage: 125.00K
Reported by: Law Enforcement