There has been a lot of farmland paved over in the past 29 years, so even a lesser rain will create equal or greater flooding.
The weather pattern is eerily similar to June of 1972 when we had a training thunderstorm event (like this one) which saturated the ground and produced some flooding—then came Agnes less than a week later.
I was a pre-teen then, and remember both vividly (born in ‘63). Yes, there is infinitely more runoff now. In addition, the communities north of Wilkes Barre are screwed, as the levee doesn’t go up that far, causing the water that would have been in WB/Kingston to instead spread out further before it gets to the levee. I’ve been seeing pics of West Pittston (where I grew up), and the waters are already as high as Agnes, with more to come.