A stretch of weak cold fronts mixed in with a deep trough of low pressure will bring an abundance of moisture to the eastern US throughout the holiday weekend. The main focus however is on Monday when rainfall is most probable at a much wider range.
The sun has been able to reach through the clouds in many areas as depicted by the visible satellite imagery of the northeast for this afternoon... Rain showers & thunderstorms for this Saturday have been secluded to the inland regions of the northeast as well as the Appalachians. These can be seen on the same visible satellite shown below by viewing the whitest clouds (for example, east of the Finger Lakes in New York).
On Monday, low pressure system associated with a deep trough will move northeast. As seen in the image below ( 12Z GFS depicting Monday afternoon), model placement of the system has it extending south through the Carolinas. While the day is not expected to be an entire washout, Monday poses the greatest threat for rain & thunderstorms over the next 3 days.
This system moves out early Tuesday & will be replaced with high pressure and an extended period of sunshine.
Enjoy the holiday weekend as best as you can.