Flash Flood in Lycoming County, Pennsylvania

Flash flooding led to the mandatory evacuation of the entire town of Glen Mawr in Shrewsbury Township. Muncy Creek rose nearly 10 feet in 3 to 4 hours at Glen Mawr.

A shortwave trough, moving through an unstable and extremely moist air mass (PWATs over 2.00) over central Pennsylvania, allowed for showers and thunderstorms to develop across the area during the afternoon hours of July 13, 2025. Thunderstorms in this environment began to become strong-to-severe; however, rainfall rates within the thunderstorms were the most notable feature, topping out over two inches per hour. The slow movement of these thunderstorms produced instances of flooding and flash flooding in York County, mainly stationed around Dover where Fox Run went over its banks and water rescues were reported. Showers and thunderstorms continued into the evening hours, where storms become anchored to higher elevation locations in Lycoming and Sullivan counties. Multiple roadways in Sullivan County were closed due to flooding and mudslides, with the nearby town of Glen Mawr (Lycoming County) being placed under a mandatory evacuation as Muncy Creek rose 10 feet in three to four hours. Flooding concerns across Sullivan and Lycoming County continued into the early morning hours of July 14, 2025 as rain began to taper off across the area.