After such a nice weekend the weather is about to take a big flip as low pressure over the south and a slow-moving cold front (thanks to a huge Atlantic ridge) will combine to make another rainfall event and a heavy one at that, this will be a long lasting system.
Showers will start to fill into the area late tnight aross western sections like into east/cental PA, and showers will slowly spread towards the coastal areas, and rain will become steady over interior areas by tomorrow afternoon
Below is early Monday morning , our cold front will be crawling eastward with waves of low pressure developing along it and moving North and showers filling in, this will be the theme through Wednesday
Going into Monday afternoon showers will start to fill in along the coastal plain and the rain will become steadier and heavier interior, especially Eastern PA
Monday night into Tuesday it all shifts east with the cold front so steady will start to shift towards the coastal plain as an area pf low pressure from the south moves up the coast, the heaviest rain inland is expected Monday through Tuesday AM and the heaviest rain along the coast is expected Tuesday morning through Wednesday morning.
Tuesday looks like a washout for the forecast area, again with everything SLOWLY shifting east, steady rain continues into Tuesday night, some embedded weak thunderstorms possible
I expect the steady heavy rain to move out early Wednesday but showers look to continue through much of the day.
I should note temperatures will be pretty mild despite rainfall due to SW flow ahead of the cold front with highs remaining in the mid 60s to mid 70s
Everyone will get a good soaking but the heaviest rain will fall over interior areas, like east and central PA
Immediate NJ coast through Long Island These will be the driest areas as a ridge over the Atlantic keeps a majority to your west, I expect overall .50-1.00 inch of rainfall from Monday afternoon through Wednesday afternoon
I95 corridor- Along the I95 corridor I expect a general 1.00-2.00 inches between Monday afternoon and Wednesday afternoon,
Western NJ / East PA – This is where we start getting into the heaviest totals, with totals ranging from 1.75 – 2.50 inches of rain locally up to 3 inches
Some flooding will be possible , no major flooding expected due to recent dry conditions and the fact that it’s a long-lasting event but some minor urban stream flooding is possible, especially in areas of PA in the heaviest rainfall
This is the HPC rain forecast, im going a bit less aggressive then them being this seems to be based off of the most agressive model, but the same general idea is shown.