A low level boundary pushed southeast ahead of an mesoscale convective system late in the afternoon. This boundary followed the passage of a warm front with effective shear values jumping to 50-60 knots as the low level boundary made its way across southern Ontario and into western New York. The evening Buffalo sounding strongly suggested that any convection would be elevated. The sounding also revealed impressively steep lapse rates through the middle levels. Supercells with strong mid-level rotation were observed over southern Ontario, and while the impressive mid level structure of the cells weakened somewhat as they dropped southeast across our area, storm tops blossomed to over 50,000 ft. As anticipated, these cells supported large hail with several reports of hail up to golf ball size. There was also tremendous lightning with the activity. As the storms moved southeast into the Southern Tier, the activity became more linear with very strong surface gusts in excess of 70 mph suggested by radar. Initially, the supercells were very efficient rain makers. While they were generating large hail, they were also producing rainfall of an inch to an inch and a half in 20-30 minutes.

Hail in ERIE, NEW YORK
From 02-JUN-20 22:13:00 to 02-JUN-20 22:13:00 (EST-5)
Location: BUFFALO
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

One inch hail was reported in Elmwood Village.

Hail in ERIE, NEW YORK
From 02-JUN-20 22:14:00 to 02-JUN-20 22:14:00 (EST-5)
Location: BUFFALO
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Thunderstorm Wind in CATTARAUGUS, NEW YORK
From 02-JUN-20 23:20:00 to 02-JUN-20 23:20:00 (EST-5)
Location: MACHIAS
Magnitude: 51.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Multiple trees were reported down.

Thunderstorm Wind in CATTARAUGUS, NEW YORK
From 02-JUN-20 23:25:00 to 02-JUN-20 23:25:00 (EST-5)
Location: WEST VLY
Magnitude: 40.00 EG
Property damage: 0.50K
Crop damage: 0.00K
Reported by: Broadcast Media

A large tree limb was downed across a driveway.

Hail in ERIE, NEW YORK
From 02-JUN-20 22:15:00 to 02-JUN-20 22:15:00 (EST-5)
Location: BUFFALO
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Hail in ERIE, NEW YORK
From 02-JUN-20 22:20:00 to 02-JUN-20 22:20:00 (EST-5)
Location: LACKAWANNA
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in CATTARAUGUS, NEW YORK
From 02-JUN-20 23:36:00 to 02-JUN-20 23:36:00 (EST-5)
Location: ELLICOTTVILLE
Magnitude: 51.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Multiple trees were reported down.

Thunderstorm Wind in ALLEGANY, NEW YORK
From 02-JUN-20 23:42:00 to 02-JUN-20 23:42:00 (EST-5)
Location: CUBA
Magnitude: 51.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Trees and wires were reported down.

Hail in ERIE, NEW YORK
From 02-JUN-20 22:43:00 to 02-JUN-20 22:43:00 (EST-5)
Location: COLDEN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Hail in ERIE, NEW YORK
From 02-JUN-20 22:47:00 to 02-JUN-20 22:47:00 (EST-5)
Location: COLDEN
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in ALLEGANY, NEW YORK
From 02-JUN-20 23:52:00 to 02-JUN-20 23:52:00 (EST-5)
Location: BOLIVAR
Magnitude: 51.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A tree was reported down.

Thunderstorm Wind in CATTARAUGUS, NEW YORK
From 02-JUN-20 23:25:00 to 02-JUN-20 23:25:00 (EST-5)
Location: ELTON
Magnitude: 53.00 MG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Mesonet

Hail in ERIE, NEW YORK
From 02-JUN-20 23:01:00 to 02-JUN-20 23:01:00 (EST-5)
Location: EAST CONCORD
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CATTARAUGUS, NEW YORK
From 02-JUN-20 23:12:00 to 02-JUN-20 23:12:00 (EST-5)
Location: YORKSHIRE
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Flash Flood in ERIE, NEW YORK
From 02-JUN-20 23:12:00 to 03-JUN-20 00:12:00 (EST-5)
Location: BUFFALO
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Sycamore Street and Walden Avenue flooded with four people trapped in a car.

Flash Flood in ERIE, NEW YORK
From 02-JUN-20 23:15:00 to 03-JUN-20 02:15:00 (EST-5)
Location: BUFFALO
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: 911 Call Center

The ramp from I-190 south to Route 198 east was closed due to flooding.

Hail in ERIE, NEW YORK
From 02-JUN-20 23:12:00 to 02-JUN-20 23:12:00 (EST-5)
Location: GLENWOOD
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Thunderstorm Wind in NIAGARA, NEW YORK
From 02-JUN-20 21:52:00 to 02-JUN-20 21:52:00 (EST-5)
Location: FALLS
Magnitude: 50.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Broadcast Media

A large tree fell on a house on 4th Street.

Flash Flood in ERIE, NEW YORK
From 02-JUN-20 23:22:00 to 03-JUN-20 01:22:00 (EST-5)
Location: SLOAN
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: 911 Call Center

I-90 was flooded at exit 51.

Hail in ERIE, NEW YORK
From 02-JUN-20 22:05:00 to 02-JUN-20 22:05:00 (EST-5)
Location: NEW FALCONWOOD
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Thunderstorm Wind in ERIE, NEW YORK
From 02-JUN-20 22:09:00 to 02-JUN-20 22:09:00 (EST-5)
Location: BUFFALO
Magnitude: 51.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: NWS Employee

Several massive 100 year old trees were downed onto Horton Place and damaged several vehicles.

Thunderstorm Wind in ERIE, NEW YORK
From 02-JUN-20 22:12:00 to 02-JUN-20 22:12:00 (EST-5)
Location: BUFFALO
Magnitude: 51.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Broadcast Media

A large tree fell onto a car on Elmwood Avenue.

Thunderstorm Wind in ERIE, NEW YORK
From 02-JUN-20 22:24:00 to 02-JUN-20 22:24:00 (EST-5)
Location: BUFFALO
Magnitude: 51.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A large tree was downed onto Clinton Street.

Thunderstorm Wind in GENESEE, NEW YORK
From 02-JUN-20 22:44:00 to 02-JUN-20 22:44:00 (EST-5)
Location: BERGER
Magnitude: 51.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A tree was reported downed onto Route 19.