A series of thunderstorms that preceded and accompanied a lee side trough and a cold front produced strong to locally severe thunderstorms mainly during the afternoon and early evening across Eastern Pennsylvania. About 6,000 PECO Energy customers lost power in southeastern Pennsylvania including Philadelphia. All power was restored by the morning of the 22nd.

Thunderstorm Wind in LEHIGH, PENNSYLVANIA
From 21-AUG-11 16:10:00 to 21-AUG-11 16:13:00 (EST-5)
Location: COPLAY
Magnitude: 56.00 EG
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

A severe thunderstorm knocked down numerous trees and tree limbs in eastern Lehigh County from Coplay Borough and Whitehall and South Whitehall Townships southward into Allentown. A concentration of downed trees was reported near the Whitehall High School. Four homes were damaged by downed trees in Whitehall Township and one in Coplay Borough. Trees were knocked down along Cedar Crest Boulevard in South Whitehall Township. In North Catasauqua, numerous large limbs were knocked down within the borough park. Tree damage occurred on the property of Saint Andrew's Roman Catholic Church and a roadway sign was flipped along Grove Street.  About 2,900 Pennsylvania Power and Light customers lost power in the county.

Lightning in MONROE, PENNSYLVANIA
From 21-AUG-11 17:00:00 to 21-AUG-11 17:00:00 (EST-5)
Location: SWIFTWATER
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Newspaper

A lightning strike caused a fire at the Swiftwater Elementary Center in Paradise Township.  The fire was contained to the roof above the third grade classrooms. It was unsure if the damage was extensive enough to delay the start of school on August 29th.

Thunderstorm Wind in MONTGOMERY, PENNSYLVANIA
From 21-AUG-11 13:10:00 to 21-AUG-11 13:10:00 (EST-5)
Location: NORTH WALES
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

A severe thunderstorm knocked down large tree limbs and wires in Upper Gwynedd Township.

Thunderstorm Wind in MONTGOMERY, PENNSYLVANIA
From 21-AUG-11 13:15:00 to 21-AUG-11 13:15:00 (EST-5)
Location: GWYNEDD
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A severe thunderstorm also knocked down large tree limbs and wires in Lower Gwynedd Township.

Thunderstorm Wind in PHILADELPHIA, PENNSYLVANIA
From 21-AUG-11 13:45:00 to 21-AUG-11 13:45:00 (EST-5)
Location: BYBERRY
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A severe thunderstorm knocked down trees and wires in northeast Philadelphia.

Thunderstorm Wind in BUCKS, PENNSYLVANIA
From 21-AUG-11 13:55:00 to 21-AUG-11 13:55:00 (EST-5)
Location: TREVOSE
Magnitude: 52.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A severe thunderstorm knocked down trees and wires in Feasterville (Lower Southampton County).

Thunderstorm Wind in BUCKS, PENNSYLVANIA
From 21-AUG-11 13:55:00 to 21-AUG-11 13:55:00 (EST-5)
Location: STANWOOD
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A severe thunderstorm knocked down large tree limbs and wires in Bensalem Township.

Hail in BUCKS, PENNSYLVANIA
From 21-AUG-11 14:00:00 to 21-AUG-11 14:00:00 (EST-5)
Location: TREVOSE
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Nickel size hail fell in Feasterville (Lower Southampton County).

Lightning in DELAWARE, PENNSYLVANIA
From 21-AUG-11 14:25:00 to 21-AUG-11 14:25:00 (EST-5)
Location: WAYNE
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Newspaper

A lightning strike and ensuing fire caused basement damage to one home on West Beechtree Lane in Radnor Township as well as a Sports Utility Vehicle next door. The lightning strike damaged a tree which fell on top of the vehicle. It then started a basement fire at the neighboring house. Four fire companies confined the smoke damage to the basement and some of the interior walls. No injuries were reported.