Flash Flood, Lebanon
- When
- July 22, 5:15 PM EST to 11:29 PM EST
- Where
- Lebanon County, 2.98 mi SE of Newmanstown to 1.35 mi ESE of Greble
- Cause
- Heavy Rain
- Reported by
- Emergency Manager
- Coordinates
- 40.322, -76.177
A record heavy rain event affected southern Lebanon County during the late afternoon and evening hours. Most of the rain fell in a 3-hour period, resulting in significant flash flooding. The estimated 3-hour rainfall rates exceeded the value for a 1000-year return period. The Quittapahilla Creek was overwhelmed by the intense rainfall, rising quickly and overflowing its banks in the city of Lebanon. The Quittapahilla Creek is a 16.8-mile-long tributary of Swatara Creek.
The pattern over much of the Mid-Atlantic region contained all of the ingredients for a significant heavy rainfall event, including above normal moisture (PWAT) and strong low-level southerly flow. Moderate instability was also a factor early in the event, with CAPE values above 1200 J/KG supporting deep moist convection.
Numerous water rescues were conducted across southern Lebanon County. The Townships that experienced the greatest flooding impacts included Londonderry, Annville, Cornwall, Lebanon, Heidelburg and Millcreek. The flash flooding transitioned into areal flooding/standing water by later in the evening and lasted into the overnight hours.