With a lot of model uncertainty still, we are going a bit on the low end. The ensembles are a good choice for making level-headed forecast in these situations. As for now, this appears a minor event. Highest totals should be in Virginia, and even there we are not expecting a thumping.
The GFS can be wonky in these kind of suppressed southern storms. One thing of higher confidence: this will not be another storm for the Northeast as it will “slide” out to sea hench the name Southern Slider.