A cold front dropped down across the region on the morning of July 21st. Convective initiation was aided by increased low-level moisture convergence along the front, as well as destabilization of the atmosphere due to daytime heating.  Convective inhibition was largely absent, and surface-based CAPE values exceeded 3000 J/kg over most of the region.  Shear was marginal, but the instability was sufficient to allow for strong to severe thunderstorms with damaging wind gusts.
A moist environment was also in place as surface dewpoints climbed into the 70s.  This, plus a flow pattern that was conducive to training thunderstorms, promoted flash flooding issues along a stalled boundary.

Flash Flood in ALLEGHENY, PENNSYLVANIA
From 21-JUL-19 21:26:00 to 21-JUL-19 22:00:00 (EST-5)
Location: ROSEDALE
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

The local emergency manager reported that Universal Road was flooded. A vehicle was stuck in water.

Flash Flood in ALLEGHENY, PENNSYLVANIA
From 21-JUL-19 21:35:00 to 21-JUL-19 22:00:00 (EST-5)
Location: ROSEDALE
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: NWS Employee

An NWS Employee reported Sandy Creek was out of its banks and flooding the intersection of Verona Rd. and Route 130.

Flash Flood in ALLEGHENY, PENNSYLVANIA
From 21-JUL-19 21:44:00 to 21-JUL-19 22:44:00 (EST-5)
Location: OPTION
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A local emergency manager reported that Washington Boulevard was closed due to flooding.

Flash Flood in ALLEGHENY, PENNSYLVANIA
From 21-JUL-19 21:51:00 to 21-JUL-19 22:51:00 (EST-5)
Location: ASPINWALL
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A local emergency manager reported that the intersection of Lincoln Avenue and Leminton Avenue was flooded. A car was stuck in the water.

Flash Flood in ALLEGHENY, PENNSYLVANIA
From 21-JUL-19 22:07:00 to 21-JUL-19 23:00:00 (EST-5)
Location: EDGEWOOD
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Public

The public reported flooding at the intersection of North Braddock Avenue and Finance Street. Cars were trapped in the water.

Thunderstorm Wind in ALLEGHENY, PENNSYLVANIA
From 21-JUL-19 13:05:00 to 21-JUL-19 13:05:00 (EST-5)
Location: IMPERIAL
Magnitude: 50.00 EG
Reported by: NWS Employee

An NWS Employee reported both trees and power lines down on Elm Street in Imperial.

Thunderstorm Wind in FAYETTE, PENNSYLVANIA
From 21-JUL-19 18:30:00 to 21-JUL-19 18:30:00 (EST-5)
Location: HOPWOOD
Magnitude: 50.00 EG
Reported by: County Official

A county official reported numerous trees down in Hopwood and Uniontown.

Flash Flood in FAYETTE, PENNSYLVANIA
From 21-JUL-19 19:00:00 to 21-JUL-19 20:00:00 (EST-5)
Location: LEITH
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: County Official

A local county official reported numerous flooded roads.

Thunderstorm Wind in BEAVER, PENNSYLVANIA
From 21-JUL-19 19:46:00 to 21-JUL-19 19:46:00 (EST-5)
Location: FRANKFORT SPGS
Magnitude: 50.00 EG
Reported by: Public

The public reported multiple trees down at Ponderosa Golf Course.

Flash Flood in WESTMORELAND, PENNSYLVANIA
From 21-JUL-19 21:43:00 to 21-JUL-19 22:43:00 (EST-5)
Location: WEST NEWTON
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Emergency Manager

The local emergency manager reported numerous roads flooded in West Newton Borough.

Flash Flood in ALLEGHENY, PENNSYLVANIA
From 21-JUL-19 21:10:00 to 21-JUL-19 22:00:00 (EST-5)
Location: NEW TEXAS
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Public

The public reported numerous roads flooded.

Thunderstorm Wind in BUTLER, PENNSYLVANIA
From 21-JUL-19 15:35:00 to 21-JUL-19 15:35:00 (EST-5)
Location: NORTH OAKLAND
Magnitude: 50.00 EG
Reported by: County Official

A county official reported trees down on Rt. 68 in Oakland Township.

Thunderstorm Wind in BEAVER, PENNSYLVANIA
From 21-JUL-19 19:47:00 to 21-JUL-19 19:47:00 (EST-5)
Location: FRANKFORT SPGS
Magnitude: 50.00 EG
Reported by: Park/Forest Service

The State Park Service reported that numerous large trees were blown down throughout Raccoon State Park.

Flash Flood in ALLEGHENY, PENNSYLVANIA
From 21-JUL-19 21:24:00 to 21-JUL-19 22:00:00 (EST-5)
Location: BLAWNOX
Flood cause: Heavy Rain
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Emergency Manager

The local emergency manager reported that  Boyd Avenue was flooded.

Flash Flood in ALLEGHENY, PENNSYLVANIA
From 21-JUL-19 21:25:00 to 21-JUL-19 22:00:00 (EST-5)
Location: HAFFEY
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Local media reported that water rescues were performed at a mobile home near Kirk Drive in Plum, which is along Plum Creek.