Flood — Lycoming, Pennsylvania

2011-09-07 to 2011-09-11 · near Picture Rocks, Lycoming, Pennsylvania

Event narrative

Loyalsock Creek at Loyalsockville crested at record/major flood level of 19.78 feet. Flood stage is 12.0 feet. The West Branch of the Susquehanna River at Muncy crested in moderate flood stage of 26.7 feet. Flood stage is 20.0 feet. This is the 9th highest crest all time. The West Branch of the Susquehanna River at Montgomery crested in moderate flood stage of 26.7 feet. Flood stage is 20.0 feet. This is the 12th highest crest all time.

Muncy Creek flooded extensive areas near Hughesville and Muncy. Residents reported the creek overflowing its banks and rushing down 5th Street flooding homes and yards. One home had its chimney and foundation washed away. Others reported extensive basement flooding. One resident just had their three-bedroom basement completely finished in January. An off-ramp off the Route 405 Bridge was washed away. Glen Mar just north of Muncy was evacuated.

The bridge on Route 220 near Hughesville is closed, though it did survive the floods. It will take several weeks before the bridge is safe to cross. Picture Rocks, also on Muncy Creek suffered extensive damage.

Route 87 on the Loyalsock Creek north of Montoursville was hard hit. Many homes outside of the 100 year flood plain reported significant flooding (and did not have flood insurance).

Evacuations along the Loyalsock and Muncy Creeks. Damage was estimated at $11,195,177 for public facilities.

Wider weather episode

Heavy rainfall from the remnants of Tropical Storm Lee produced widespread flooding, flash flooding and river flooding mainly near and to the east of the Susquehanna Valley from September 4-10. Several locations in the Susquehanna Basin came close to records set by Hurricane Agnes (June 1972) and a few points (Bloomsburg, Hershey and Loyalsockville) set new floods of record. Flooding along Swatara Creek resulted in property damage and several deaths. Severe flooding occurred along Loyalsock Creek and many points along the main-stem of the Susquehanna River. The interaction of a stalled frontal boundary over the Mid-Atlantic region, a strong northern stream short-wave (with a persistent jet entrance region) and deep tropical moisture associated the remnants of Tropical Storm Lee resulted in multi-day, significant heavy rainfall event over Pennsylvania.

Tropical storm Lee was the twelfth named storm of the 2011 season forming over the Gulf of Mexico on September 1. A strong northern stream short-wave interacted with Lee causing the storm to re-curve to the north-northeast. By 1200 UTC September 6, having undergone extra-tropical transition, post-tropical Lee was located over northern Georgia. The surface low weakened as it moved up the Appalachian Mountain chain. However, the strong low-level flow and the above normal precipitable water produced an extensive, north-to-south oriented band of heavy rainfall.

The rainfall associated with the remnants of Lee produced the 4th largest flood of record in the Mid-Atlantic Region. The five-day storm rainfall totals for September 5 to 9 were generally in the 5-8 inch range over the mid-section of central Pennsylvania and in the 8-12 inch range in the Susquehanna Valley region. There were local amounts reported in excess of 15 inches east of the Susquehanna River. The local climate sites in Harrisburg (KMDT) and Williamsport (KIPT) reported 13.44 and 9.03 inches respectively. On September 7, 2011 both KMDT and KIPT set their all-time daily (24-hour) rainfall for the month of September at 7.71 and 6.76 inches respectively. These sites later went on to break the all-time monthly (September) and annual precipitation records, making 2011 the wettest year on record.

View location on OpenStreetMap → (41.2759, -76.7024)

Source: NOAA Storm Events Database, event_id 348393. Narrative written by the NWS forecast office that issued the report.