Rain, fog, and thunderstorms tonight, clearing and windy Saturday
Today has seen a strong temperature gradient across the region. Out ahead of a cold front, there has been a persistent southerly flow, which has helped to warm the airmass. It has also allowed for a strong temperature gradient to form, as from NYC and westward, temperatures are in the 60s, but east of NYC, temperatures are primarily stuck in the upper 40s to low 50s with dense fog.
This is because as you go further east, the southerly winds have a strong fetch from the frigid Atlantic Ocean. This helps to cool temperatures off substantially in Long Island. Given that the airmass as a whole is somewhat warm and muggy, the cold low-level temperatures on Long Island end up being much closer to their dewpoints, which means a much more saturated low-level atmosphere. This has helped to create dense fog on Long Island, and this is expected to last for the rest of the day and night.
Further west, with surface temperatures a bit warmer but in the same airmass, fog will be patchy, but not as dense as it will be on Long Island.
As far as the rain is concerned, while a few scattered showers are possible during the next few hours, the area will be primarily rain-free for the evening and early-overnight, save for some fog-related drizzle. After midnight is when rain and some embedded thunderstorms could return.