From the National Weather Service:

The West Branch of the Susquehanna River at Williamsport, Pa is forecast to crest Saturday morning at 14 and one-half feet.  This would be 4 feet over the action level, but well below the minor flood level of 20 feet. 

This high water is a result of snow melt from recent warm days and rainfall Thursday night.

See more weather information at http://www.weather.gov/ctp/