A cold front dropped from north to south across the area. Unstable conditions were evident ahead of this, with about 2000 J/kg CAPE developing by late afternoon. Moderate mid-level shear was present with a shortwave just ahead of the front. Storms developed ahead of this frontal boundary around 3 PM and along a lake breeze boundary in Niagara County. Impressive cores aloft were quickly evident as they developed. These cells kept redeveloping back to the west, with several impressive cores aloft prompting multiple warnings. These produced numerous reports of large hail, including tennis ball sized hail Storms also trained along the boundary, producing heavy rainfall in the same location. This produced significant flash flooding in Lockport and surrounding areas. Otherwise, a line closer to the front moved across southern Ontario and across Lake Ontario and the St Lawrence River into the eastern Lake Ontario region. These storms mainly produced wind damage more than hail. Lingering more marginal storms across western New York just ahead the front caused some wind damage.

Thunderstorm Wind in JEFFERSON, NEW YORK
From 20-JUL-21 15:27:00 to 20-JUL-21 15:27:00 (EST-5)
Location: ALEXANDRIA BAY ARPT
Magnitude: 51.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Public

Trees and wires were reported down.

Thunderstorm Wind in JEFFERSON, NEW YORK
From 20-JUL-21 15:25:00 to 20-JUL-21 15:25:00 (EST-5)
Location: CLAYTON
Magnitude: 51.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Public

Trees and wires were reported down.

Thunderstorm Wind in NIAGARA, NEW YORK
From 20-JUL-21 16:51:00 to 20-JUL-21 16:51:00 (EST-5)
Location: PENDLETON CENTER
Magnitude: 51.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Trees were reported down.

Thunderstorm Wind in OSWEGO, NEW YORK
From 20-JUL-21 17:00:00 to 20-JUL-21 17:00:00 (EST-5)
Location: PENNELLVILLE
Magnitude: 51.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Public

Trees and wires were reported down.

Thunderstorm Wind in JEFFERSON, NEW YORK
From 20-JUL-21 15:43:00 to 20-JUL-21 15:43:00 (EST-5)
Location: PLESSIS
Magnitude: 51.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

A utility pole and tree were both down onto Hunter Road.

Thunderstorm Wind in JEFFERSON, NEW YORK
From 20-JUL-21 15:58:00 to 20-JUL-21 15:58:00 (EST-5)
Location: ANTWERP
Magnitude: 51.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Trees and wires were reported down.

Thunderstorm Wind in LEWIS, NEW YORK
From 20-JUL-21 17:31:00 to 20-JUL-21 17:31:00 (EST-5)
Location: BRANTINGHAM
Magnitude: 51.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Public

Trees and wires were reported down.

Thunderstorm Wind in LEWIS, NEW YORK
From 20-JUL-21 17:42:00 to 20-JUL-21 17:42:00 (EST-5)
Location: LYONSDALE
Magnitude: 51.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Trees and wires were reported down.

Hail in NIAGARA, NEW YORK
From 20-JUL-21 15:34:00 to 20-JUL-21 15:34:00 (EST-5)
Location: SOUTH LOCKPORT
Magnitude: 1.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in NIAGARA, NEW YORK
From 20-JUL-21 15:35:00 to 20-JUL-21 15:35:00 (EST-5)
Location: CARLISLE GARDENS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: CoCoRaHS

Thunderstorm Wind in LEWIS, NEW YORK
From 20-JUL-21 17:42:00 to 20-JUL-21 17:42:00 (EST-5)
Location: TALLCOTTVILLE
Magnitude: 51.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Trees and wires were reported down.

Flash Flood in NIAGARA, NEW YORK
From 20-JUL-21 18:03:00 to 20-JUL-21 21:03:00 (EST-5)
Location: ECHOTA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Flash flooding was reported on Military Road.

Hail in NIAGARA, NEW YORK
From 20-JUL-21 15:43:00 to 20-JUL-21 15:43:00 (EST-5)
Location: CARLISLE GARDENS
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in NIAGARA, NEW YORK
From 20-JUL-21 15:51:00 to 20-JUL-21 15:51:00 (EST-5)
Location: BLAIRVILLE
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Flash Flood in NIAGARA, NEW YORK
From 20-JUL-21 20:30:00 to 20-JUL-21 21:00:00 (EST-5)
Location: VETERANS HGTS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Route 265 was closed due to flooding between Route 182 and Lockport Road.

Thunderstorm Wind in ONTARIO, NEW YORK
From 20-JUL-21 18:55:00 to 20-JUL-21 18:55:00 (EST-5)
Location: CLIFTON SPGS
Magnitude: 51.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Two trees were reported down onto County Road 13.

Hail in NIAGARA, NEW YORK
From 20-JUL-21 15:41:00 to 20-JUL-21 15:41:00 (EST-5)
Location: CAMBRIA
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in NIAGARA, NEW YORK
From 20-JUL-21 16:05:00 to 20-JUL-21 16:05:00 (EST-5)
Location: LEWISTON HGTS
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm Wind in ONTARIO, NEW YORK
From 20-JUL-21 19:03:00 to 20-JUL-21 19:03:00 (EST-5)
Location: PHELPS
Magnitude: 51.00 EG
Property damage: 0.50K
Crop damage: 0.00K
Reported by: 911 Call Center

A tree was reported down onto Wheat Road.

Thunderstorm Wind in ERIE, NEW YORK
From 20-JUL-21 17:52:00 to 20-JUL-21 17:52:00 (EST-5)
Location: EAST AMHERST
Magnitude: 51.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Trees were reported down.

Hail in NIAGARA, NEW YORK
From 20-JUL-21 16:07:00 to 20-JUL-21 16:07:00 (EST-5)
Location: SOUTH LOCKPORT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in NIAGARA, NEW YORK
From 20-JUL-21 16:13:00 to 20-JUL-21 16:13:00 (EST-5)
Location: SOUTH LOCKPORT
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm Wind in CATTARAUGUS, NEW YORK
From 20-JUL-21 19:53:00 to 20-JUL-21 19:53:00 (EST-5)
Location: SANDUSKY
Magnitude: 51.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Trees were reported down.

Thunderstorm Wind in CATTARAUGUS, NEW YORK
From 20-JUL-21 19:36:00 to 20-JUL-21 19:36:00 (EST-5)
Location: OLEAN
Magnitude: 51.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Multiple reports of trees down were received.

Hail in NIAGARA, NEW YORK
From 20-JUL-21 16:13:00 to 20-JUL-21 16:13:00 (EST-5)
Location: LEWISTON HGTS
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in NIAGARA, NEW YORK
From 20-JUL-21 15:58:00 to 20-JUL-21 15:58:00 (EST-5)
Location: CAMBRIA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm Wind in CATTARAUGUS, NEW YORK
From 20-JUL-21 19:42:00 to 20-JUL-21 19:42:00 (EST-5)
Location: PORTVILLE
Magnitude: 51.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Multiple reports of trees down were received.

Thunderstorm Wind in ALLEGANY, NEW YORK
From 20-JUL-21 19:57:00 to 20-JUL-21 19:57:00 (EST-5)
Location: BOLIVAR
Magnitude: 51.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Trees were reported down.

Hail in NIAGARA, NEW YORK
From 20-JUL-21 15:57:00 to 20-JUL-21 15:57:00 (EST-5)
Location: LOCKPORT
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Flash Flood in NIAGARA, NEW YORK
From 20-JUL-21 16:37:00 to 20-JUL-21 19:37:00 (EST-5)
Location: SOUTH LOCKPORT
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Public

Road closures were reported due to flooding with vehicles stranded in the streets.

Thunderstorm Wind in ALLEGANY, NEW YORK
From 20-JUL-21 20:16:00 to 20-JUL-21 20:16:00 (EST-5)
Location: WELLSVILLE
Magnitude: 51.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Trees were reported down.

Thunderstorm Wind in CHAUTAUQUA, NEW YORK
From 20-JUL-21 21:52:00 to 20-JUL-21 21:52:00 (EST-5)
Location: CASSADAGA
Magnitude: 51.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Trees and wires were reported down on Putnam Road.

Thunderstorm Wind in OSWEGO, NEW YORK
From 20-JUL-21 17:23:00 to 20-JUL-21 17:23:00 (EST-5)
Location: CONSTANTIA
Magnitude: 60.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Widespread damage was reported with numerous trees and wires down.

Flash Flood in NIAGARA, NEW YORK
From 20-JUL-21 16:50:00 to 20-JUL-21 19:50:00 (EST-5)
Location: LOCKPORT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

High Street was closed due to flooding.

Flash Flood in NIAGARA, NEW YORK
From 20-JUL-21 16:50:00 to 20-JUL-21 19:50:00 (EST-5)
Location: LOCKPORT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Market Street was flooded and closed.

Thunderstorm Wind in CHAUTAUQUA, NEW YORK
From 20-JUL-21 21:40:00 to 20-JUL-21 21:40:00 (EST-5)
Location: BROCTON
Magnitude: 51.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Trees were reported down on Route 380.

Thunderstorm Wind in CATTARAUGUS, NEW YORK
From 20-JUL-21 22:30:00 to 20-JUL-21 22:30:00 (EST-5)
Location: LEON
Magnitude: 51.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Multiple reports of trees down were received.

Flash Flood in NIAGARA, NEW YORK
From 20-JUL-21 17:20:00 to 20-JUL-21 20:20:00 (EST-5)
Location: PEKIN
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Water was flowing across the road on Town Line Road at Lower Mountain Road.

Flash Flood in NIAGARA, NEW YORK
From 20-JUL-21 17:28:00 to 20-JUL-21 20:28:00 (EST-5)
Location: CAMBRIA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Water and debris was flowing over Blackman Road.

Thunderstorm Wind in CATTARAUGUS, NEW YORK
From 20-JUL-21 23:21:00 to 20-JUL-21 23:21:00 (EST-5)
Location: OLEAN
Magnitude: 51.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Trees and wires were reported down in multiple locations around Olean.

Thunderstorm Wind in NIAGARA, NEW YORK
From 20-JUL-21 16:24:00 to 20-JUL-21 16:24:00 (EST-5)
Location: DYSINGER
Magnitude: 51.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Trees were reported downed.

Flash Flood in NIAGARA, NEW YORK
From 20-JUL-21 17:28:00 to 20-JUL-21 20:28:00 (EST-5)
Location: LOCKPORT
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Public

Additional reports of widespread flooding were received with stranded vehicles in other portions of Lockport.

Flash Flood in NIAGARA, NEW YORK
From 20-JUL-21 19:10:00 to 20-JUL-21 21:10:00 (EST-5)
Location: SOUTH LOCKPORT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

A state of emergency was issued that included a travel ban due to widespread flooding in Niagara County.

Flood in NIAGARA, NEW YORK
From 20-JUL-21 23:47:00 to 21-JUL-21 00:47:00 (EST-5)
Location: MOLYNEAUX CORNERS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Flooding was reported on Green Road.

Flash Flood in NIAGARA, NEW YORK
From 20-JUL-21 18:45:00 to 20-JUL-21 20:45:00 (EST-5)
Location: CAMBRIA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

Route 425 was reported to be closed between Lower and Upper Mountain Roads.

Thunderstorm Wind in LEWIS, NEW YORK
From 20-JUL-21 17:08:00 to 20-JUL-21 17:08:00 (EST-5)
Location: NEW BREMEN DUFLO ARP
Magnitude: 51.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Trees and wires were reported down.

Hail in NIAGARA, NEW YORK
From 20-JUL-21 15:06:00 to 20-JUL-21 15:06:00 (EST-5)
Location: CAMBRIA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm Wind in OSWEGO, NEW YORK
From 20-JUL-21 16:55:00 to 20-JUL-21 16:55:00 (EST-5)
Location: ORWELL
Magnitude: 51.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Widespread damage was reported in Orwell, including numerous trees and wires down.

Thunderstorm Wind in OSWEGO, NEW YORK
From 20-JUL-21 17:10:00 to 20-JUL-21 17:10:00 (EST-5)
Location: AMBOY CENTER
Magnitude: 51.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Widespread damage was reported in the Town of Amboy.

Hail in NIAGARA, NEW YORK
From 20-JUL-21 17:02:00 to 20-JUL-21 17:02:00 (EST-5)
Location: LEWISTON HGTS
Magnitude: 2.50 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Tennis ball sized hail was reported in Lewiston.

Thunderstorm Wind in OSWEGO, NEW YORK
From 20-JUL-21 16:52:00 to 20-JUL-21 16:52:00 (EST-5)
Location: PHOENIX
Magnitude: 60.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: 911 Call Center

Widespread damage was reported with numerous trees and wires down.