A surface low moved east-southeastward from northwestern Lower MI to the southeastern shore of Lake Huron during the late morning through mid-evening of the 20th. Simultaneously, the low's warm front swept northeastward across northwestern PA to central Lake Ontario and central NY, and the low's trailing cold front moved generally eastward from northwestern Lower MI and southern Lake Michigan to southern Lake Huron and near the western shore of Lake Erie. Moderate to strong MUCAPE and effective bulk shear, respectively, were present just ahead of the surface warm front and within the warm sector.
A multicell thunderstorm in vicinity of the surface warm front persisted northeastward across northern portions of Erie County, including the city of Erie, during the early afternoon and produced severe hail and damaging convective wind gusts. A semi-discrete supercell then moved generally eastward across southern Erie County during the late afternoon through early evening and produced severe hail, including large hail of 2-inches in diameter in the Corry area. Following the supercell, a line of multicell thunderstorms persisted generally eastward and southeastward across northwest Pennsylvania and produced isolated straight-line convective wind damage in Conneautville, Crawford County.

Hail in ERIE, PENNSYLVANIA
From 20-JUL-23 17:05:00 to 20-JUL-23 17:05:00 (EST-5)
Location: UNION CITY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Hail up quarter-size about one-mile west of Union City.

Hail in ERIE, PENNSYLVANIA
From 20-JUL-23 12:39:00 to 20-JUL-23 12:39:00 (EST-5)
Location: ERIE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail up to quarter-size in Erie.

Hail in ERIE, PENNSYLVANIA
From 20-JUL-23 12:43:00 to 20-JUL-23 12:43:00 (EST-5)
Location: LAWRENCE PARK
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail up to half dollar-size about three-miles ENE of downtown Erie.

Hail in ERIE, PENNSYLVANIA
From 20-JUL-23 17:08:00 to 20-JUL-23 17:08:00 (EST-5)
Location: ELGIN
Magnitude: 1.00 
Property damage: 7.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail up to quarter-size damaged vehicles and tore through window screens in Elgin.

Hail in ERIE, PENNSYLVANIA
From 20-JUL-23 17:29:00 to 20-JUL-23 17:29:00 (EST-5)
Location: CORRY
Magnitude: 2.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail up to hen egg-size in Corry.

Thunderstorm Wind in CRAWFORD, PENNSYLVANIA
From 20-JUL-23 18:18:00 to 20-JUL-23 18:18:00 (EST-5)
Location: CONNEAUTVILLE
Magnitude: 55.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Trees downed in Conneautville.

Thunderstorm Wind in ERIE, PENNSYLVANIA
From 20-JUL-23 12:43:00 to 20-JUL-23 12:43:00 (EST-5)
Location: LAWRENCE PARK
Magnitude: 55.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Several large trees downed about three-miles ENE of downtown Erie.

Hail in ERIE, PENNSYLVANIA
From 20-JUL-23 12:42:00 to 20-JUL-23 12:42:00 (EST-5)
Location: ERIE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Hail up to quarter-size at Presque Isle State Park in Erie.

Hail in ERIE, PENNSYLVANIA
From 20-JUL-23 16:06:00 to 20-JUL-23 16:06:00 (EST-5)
Location: GIRARD
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail up to nickel-size in Girard.

Hail in ERIE, PENNSYLVANIA
From 20-JUL-23 16:08:00 to 20-JUL-23 16:08:00 (EST-5)
Location: GIRARD
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail up to quarter-size one-mile ENE of Girard.

Hail in ERIE, PENNSYLVANIA
From 20-JUL-23 16:31:00 to 20-JUL-23 16:31:00 (EST-5)
Location: BRANCHVILLE
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail up to ping pong ball-size about three-miles south of McKean.