It is the manner in which it achieves the BM position that is causing the eastward look to the precip compared to a more conventional storm.....typically storms move northeast or ENE to the BM....but this one is kind of taking a wider turn to the right and then hooking north....when it does that, the heavier WCB precip is not going to get western areas as much...it comes up through the Cape and eastern areas first and then you have to wait until the CCB backs in from the E or SE.
The compactness of this storm will definitely be somethign to watch....if it's a bit wider circulation, then you will do fine with a BM track...but if it implodes a bit toward the center, then we could see an annoying dropoff in totals west of roughly ORH-IJD.