It wasn't that long ago that (most of) the state received a drought-bending rain event. Tonight begins the next one, which looks to have an even better setup for a widespread significant rain event. This discussion will focus on that.
This is probably the best rainfall setup we can get aside from a tropical system directly impacting us. It's a lot like the previous rain setup, with a key difference.
Part One--the cold front that will bring cooler temperatures to start the week is sagging through the region now, bringing us rainfall. I've already received .20" here in central CT! This boundary will slowly slide south and stall out over southern New England. This is critical as it will serve as the focal point for rainfall the next two days.
Part Two--tomorrow with the front stalled in the region, we will see moisture advected toward the state. This will be an anomalous amount of moisture that allows for more efficient rainfall. We'll see rain showers redevelop in the morning, and during the afternoon the coverage and intensity of the rain will pick up. This should be a widespread moderate to heavy rain that washes out our Labor Day afternoon.
Part Three--this is the trickiest part of the forecast. Even by itself, we should see Monday rain totals on the order of .50"-1" of rainfall with any errors on the higher side (meaning you are likely to get more rain than less). On Tuesday, we should see an area of low pressure develop along the front and this should provide a boost through the day. If there are higher end rain totals to be had, it's here.
Here's the 12z Euro depiction below.
My forecast is for a general 1-3" of rain between this evening and Tuesday night. I think northern CT has the best chance of overproducing, with SW CT in the danger zone again if the boundary doesn't drag far enough south.
As you will see below, if the Tuesday coastal materializes some even higher end totals are possible in parts of the state.
Images below courtesy of Weathermodels.com
Although the GFS tries to keep the rain going into Wednesday, I think that is overdone. The low and boundary should continue to sag south, leaving clearing as we get to the middle of the week.
Highs on Monday and Tuesday should be in the low 70s, but we will see clearing conditions and temperatures rebound as we get toward the end of the week and weekend. Nothing terribly warm.